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THE DL POLY 2 USER MANUAL W. Smith and T.R. Forester

1. with the force on atom i the negative of this The contribution to the atomic virial is 1 NM Ww mi 2 114 4T 0 Tjj which is simply the negative of the potential term The contribution to be added to the atomic stress tensor is are 2 115 where o f are x y z components The atomic stress tensor is symmetric In DL_POLY_2 these forces are handled by the routines COULO and COULONEU OCCLRC 48 2 4 3 Truncated and Shifted Coulomb Sum This form of the Coulomb sum has the advantage that it drastically reduces the range of electrostatic interactions without giving rise to a violent step in the potential energy at the cutoff Its main use is for preliminary preparation of systems and it is not recommended for realistic models The form of the potential function is U rij 995 i 2 116 Am 0 Ti Tout with qe the charge on an atom labelled Teut the cutoff radius and r the magnitude of the separation vector dup cuf The force on an atom j derived from this potential within the radius reyz is l 99 Gm 1 5 2 117 J Arme 7j x with the force on atom i the negative of this The contribution to the atomic virial is which is not the negative of the potential term in this case The contribution to be added to the atomic stress tensor is given by n 2 119 where o f are x y z components The atomic stress tensor is symmetric In DL_POLY_2 these forces are handled by the rou
2. 1 dij U r 2 124 rij Anege ri Tjj with qe the charge on an atom labelled and r the magnitude of the separation vector Tg on e r is the distance dependent dielectric function In DL POLY 2 it is assumed that this function has the form e r er 2 125 where e is a constant Inclusion of this term effectively accelerates the rate of convergence of the Coulomb sum The force on an atom j derived from this potential is l qa LL 2 126 Lj 2T 0 rij with the force on atom i the negative of this The contribution to the atomic virial is which is 2 times the potential term The contribution to be added to the atomic stress tensor is given by gie EI 2 128 where o f are x y z components The atomic stress tensor is symmetric In DL_POLY_2 these forces are handled by the routines COUL2 and COUL2NEU CCLRC 50 2 4 5 Ewald Sum The Ewald sum 10 is the best technique for calculating electrostatic interactions in a periodic or pseudo periodic system The basic model for a neutral periodic system is a system of charged point ions mutually interacting via the Coulomb potential The Ewald method makes two amendments to this simple model Firstly each ion is effectively neutralised at long range by the superposition of a spherical gaussian cloud of opposite charge centred on the ion The combined assembly of point ions and gaussian charges becomes the Real Space part of the Ewald sum which
3. CCLRC 158 41 42 43 44 Smith W 1991 Comput Phys Commun 62 229 Smith W 1993 Theoretica Chim Acta 84 385 Smith W 1992 Comput Phys Commun 67 392 Vessal B Amini M Leslie M and Catlow C R A 1990 Molecular Simulation 5 1 Appendix A The DL POLY 2 Makefile i Master makefile for DL POLY 2 0 Author W Smith November 1999 With DPP tool by J Geronowicz Original by T Forester 1995 Author wl Date 2000 01 17 17 01 09 Revision 1 8 State Exp Define default settings FFTW LIBRARY BINROOT execute CC cc DPP dpp EX DLPOLY X EXE BINROOT EX FC undefined PVM EX V EX V SHELL bin sh STRESS STRESS TYPE 3pt Define object files 159 OCCLRC 160 OBJ_ALL angfrc o bndfrc o cfgscan o corshl o coul0 o coul4 o coul2 o coul3 o conscan o dblstr o dcell o diffsn0 o A diffsni o dlpoly o duni o error o ewaldl o ewald3 o exclude o exclude_atom o fldscan o exclude_link o exitcomms o extnfld o fbpfrc o fcap o forces o freeze o gauss o gdsum o getrec o gimax o gisum o gstate o images o initcomms o intlist o intstr o invert o invfrc o jacobi o lowcase o lrcmetal o A lrcorrect o machine o merge o mergei o merge4 o multiple o multiple nsq o npt bi o npt b3 o parset o npt_hi o npt_h3 o nve 1 0 A nvt bi o nvt_el o nvt_hl o parlst nsq o parlink o parlst o passcon o V passpmf o pmf 1 0 pmf shake o priml
4. 4 1 3 4 External Field The presence of an external field is flagged by the extern directive The next line in the FIELD file should have another directive indicating what type of field is to be applied On the following lines comes the mxf1d parameters five per line that describe the field In the include files supplied with DL_POLY_2 mxf1d is set to 10 The variables pertaining to each potential are described in table 4 15 4 1 3 5 Closing the FIELD File The FIELD file must be closed with the directive close which signals the end of the force field data Without this directive DL_POLY_2 will abort 4 1 4 The REVOLD File This file contains statistics arrays from a previous job It is not required if the current job is not a continuation of a previous run ie if the restart directive is not present in the CONTROL file see above The file is unformatted and therefore not readable by normal people DL POLY 2 normally produces the file REVIVE see section 4 2 4 at the end of a job which contains the statistics data REVIVE should be copied to REVOLD before a continuation run commences This may be done by the copy macro supplied in the execute sub directory of DL POLY 2 CCLRC 122 4 1 4 1 Format The REVOLD file is unformatted All variables appearing are written in native real 8 representation Nominally integer quantities e g the timestep number nstep are repre sented by the the nearest real number The contents are a
5. Action There is no fix for this In any case it does not make sense to use the RESPA algorithm for this purpose Message 513 error SPME not available for given boundary conditions The SPME algorithm in DL POLY 2 does not work for aperiodic IMCON 0 or slab IMCON 6 boundary conditions Action If the system must have aperiodic or slab boundaries nothing can be done In the latter case however it may be acceptable to represent the same system with slabs replicated in the z direction thus permitting a periodic simulation CCLRC 216 Message 514 error SPME routines have not been compiled in The inclusion of the SPME algorithm in DL_POLY_2 is optional at the compile stage If the executable does not contain the SPME routines but the method is requested by the user this error results Action DL_POLY_2 must be recompiled with the SPME flags set Beware that your system has the necessary fast Fourier transform routines to permit this
6. bim do 2 103 CCLRC 45 2 Harmonic cosine hcos U dijkn S cos digan cos do 2 104 3 Planar potential plan U ijkn A 1 cos ijkn 2 105 These functions are identical to those appearing in the intra molecular inversion angle descriptions above There are significant differences in implementation however arising from the fact that the four body potentials are regarded as inter molecular Firstly the atoms involved are defined by atom types not specific indices Secondly there are no excluded atoms arising from the four body terms The inclusion of other potentials for example pair potentials may in fact be essential to maintain the structure of the system The four body potentials are very short ranged typically of order 3 This property plus the fact that four body potentials scale as N where N is the number of particles makes it essential that these terms are calculated by the link cell method 29 The calculation of the forces virial and stress tensor described in the section on inversion angle potentials above DL POLY 2 applies no long range corrections to the four body potentials The four body forces are calculated by the routine FBPFRC 2 3 5 External Fields In addition to the molecular force field DL POLY 2 allows the use of an external force field Examples of field available include 1 Electric field elec Fi Fictq H 2 106 2 Oscillating shear os
7. c ewald sum or ewald precision or coul or shift or distan or reaction or no elec specifying the required coulombic forces option d cut and delr specifying the short range forces cutoff and Verlet strip CCLRC 104 e prim specifying primary forces cutoff if mult gt 2 only 2 The job time and close time directives are required to ensure a controlled close down procedure when a job runs out of time The time specified by the job time directive indicates the total time allowed for the job This must obviously be set equal to the time specified to the operating system when the job is submitted The close time directive represents the time DL_POLY_2 will require to write and close all the data files at the end of processing This means the effective processing time limit is equal to the job time minus the close time Thus when DL_POLY_2 reaches the effective job time limit it begins the close down procedure with enough time in hand to ensure the files are correctly written In this way you may be sure the restart files etc are complete when the job terminates Note that setting the close time too small will mean the job will crash before the files have been finished If it is set too large DL_POLY_2 will begin closing down too early How large the close time needs to be to ensure safe close down is system dependent and a matter of experience It generally increases with the job size 3 The starting options for a simulation are gover
8. q093 2 q1q3 9092 R 2 q192 9093 q6 4i 4 42 43 2 q293 q091 2 186 2 qiq3 9092 2 q943 04 46 4i 92 Q3 so that if d is the position of a site in the local body frame with respect to its centre of mass its position in the space fixed frame w r t its centre of mass is given by d R d 2 187 2 5 6 2 Integration of the Rigid Body Equations of Motion The net translational force acting upon the rigid unit is F 5 des 2 188 Q where f is the force on a rigid unit site and the sum includes all sites a in the body The translational motion can be integrated by the standard leapfrog algorithm V t4 At e lie At AtM AE 2 189 An alternative approach is to define basic and secondary particles The basic particles are the minimun number needed to define a local body axis system The remaining particle positions are expressed in terms of the c o m and the basic particles Ordinary bond constraints can then be applied to the basic particles provided the forces and torques arising from the secondary particles are transferred to the basic particles in a physically meaningful way CCLRC 67 X t4 At X At V 14 25 2 190 where M is the mass of the rigid unit V is the rigid bodies c o m velocity and X is the c o m position The cartesian components of these quantitites are stored in the arrays gvxx gvyy and gvzz for c o m velocity and gcmx gcmy and gcmz for c o
9. which is recognisable as a sum of pair forces for example the force on atom j due to the which gives atom 2 a 4 Cm 1 2 1 2 a a 1 esee LO NER Hos Prag i EE gt fis 2 90 2 A ju 2 90 where rj rj rj The force on atom i is the negative of this With the pair forces thus defined the contribution to be added to the atomic virial from each atom pair is then The contribution to be added to the atomic stress tensor is given by ga gap 2 92 where o and f indicate the x y z components The atomic stress tensor is symmetric CCLRC 43 The long range correction for the system potential is in two parts Firstly by analogy with the short ranged potentials the correction to the local density is obtained by oo a m pi pp 4p 5 r dr 2 93 Tout NT where p is the uncorrected local density and p is the mean particle density Evaluating the integral yields 2 z m dp a 2 2 94 m 3 Teut which is the local density correction and is identical for all atoms The correction is applied immediately after the local density is calculated The density term of the Sutton Chen potential needs no further correction The pair term correction is obtained by analogy with the short ranged potentials and is N epa a e U 27 2 corr in 3 95 The correction to the local density having already been applied To estimate the virial correction we assume the corrected local densities are cons
10. 10 inversions n where n is the number of inversion interactions present in the molecule Each of the following n records contains inversion key ad potential key See table 4 10 index 1 integer first atomic index CCLRC 11 12 index 2 index 3 index 4 variable 1 variable 2 integer integer integer real real 118 second atomic index third atomic index fourth atomic index potential parameter see table 4 10 potential parameter see table 4 10 The meaning of the variables 1 2 is given in table 4 10 This directive and associated data records need not be specified if the molecule contains no inversion angle terms See the note on the atomic indices appearing under the shell directive above 14 is the rigid n Table 4 10 Inversion Angle Potentials potential type Variables 1 2 functional formi Harmonic Harmonic cosine Planar inversion angle U 3k do U 4 cos cos o where n is the number of rigid units in the molecule It is followed by at least n records each specifying the sites in a rigid unit m site 1 site 2 site 3 site m integer integer integer integer integer number of sites in rigid unit first site atomic index second site atomic index third site atomic index etc m th site atomic index Up to 15 sites can be specified on the first record Additional records are used if necessary Up to 16 sites are specified per record thereafte
11. 4pt check 0BJ ALL 0BJ_4PT OBJ_NEU OBJ_RIG OBJ_EXT TIMER OBJ_SPME LD EXE OBJ_ALL OBJ_4PT OBJ_NEU OBJ_RIG OBJ_EXT TIMER LDFLAGS LDLIBS OBJ_SPME Force tables interpolation in r squared rsq check 0BJ ALL 0BJ RSQ 0BJ NEU OBJ_RIG 0BJ EXT TIMER 0BJ_SPME LD EXE 0BJ ALL OBJ_RSQ 0BJ NEU 0BJ RIG 0BJ EXT TIMER LDFLAGS LDLIBS OBJ_SPME Check that a machine has been specified check if test FC undefined then echo You must specify a target machine Clean up the source directory clean rm f 0BJ ALL 0BJ RRR 0BJ EXT 0BJ NEU OBJ_RIG TIMER OBJ_SPME 0BJ_4PT OBJ_RSQ tmp f mpif h Compile preprocessor code dpp dpp c CC dpp c o dpp Declare dependencies c preprocess all f files f o DPP CPFLAGS f gt tmp f FC FFLAGS tmp f mv tmp o o C 0 CC c c Declare dependency on parameters file 0BJ_ALL dl_params inc CCLRC OBJ_RRR OBJ_4PT OBJ_RSQ OBJ_NEU OBJ_RIG OBJ_EXT 0BJ_SPME dl params inc dl params dl params dl params dl params dl params dl params inc inc inc inc inc inc 169 Appendix B Periodic Boundary Conditions in DL_POLY Introduction DL_POLY_2 is designed to accommodate a number of different periodic boundary condi tions which are defined by the
12. EWALD4 The first of these calculates the real space contribution the second the self interaction corrections and the third is required for the multiple timestep option 2 6 5 Three Body Forces DL POLY 2 can calculate three body interactions of the valence angle type 44 These are not dealt with in the same way as the normal nonbonded interactions They are generally very short ranged and are most effectively calculated using a link cell scheme 23 No reference is made to the Verlet neighbour list nor the excluded atoms list It follows that atoms involved in the same three body term can interact via nonbonded pair forces and ionic forces also The calculation of the three body terms is distributed over processors on the basis of the identity of the central atom in the bond A global summation is required to specify the atomic forces fully 2 6 6 Metal Potentials The simulation of metals by DL_POLY_2 makes use of density dependent potentials of the Sutton Chen type 6 The dependence on the atomic density presents no difficulty however as this class of potentials can be resolved into pair contributions This permits the use of the distributed Verlet neighbour list outlined above 2 6 7 Summing the Atomic Forces The final stage in the RD strategy is the global summation of the atomic force arrays This must be done After all the contributions to the atomic forces have been calculated To do this DL POLY 2 employs a global summation
13. REVIVE and gopoly all variants It is useful for cleaning the sub directory up after a run Useful data should be stored elsewhere however 6 1 2 3 copy copy invokes the unix commands mv CONFIG CONFIG OLD mv REVCON CONFIG mv REVIVE REVOLD which collectively prepare the DL POLY files in the execute sub directory for the continu ation of a simulation It is always a good idea to store these files elsewhere in addition to using this macro CCLRC 148 6 1 2 4 gopoly gopoly is used to submit a DL_POLY job to the Daresbury IBM SP 2 which operates a LOADLEVELLER job queuing system It invokes the following script 0 min processors 4 0 max processors 4 job_type parallel requirements Adapter hps_ip amp amp Pool 2 executable usr bin poe cpu_limit 00 10 00 arguments dl_poly_2 10 execute DLPOLY X euilib ip output gopoly o error gopoly e class dev queue Using LOADLEVELLER the job is submitted by the unix command llsubmit gopoly where Ilsubmit is a local command for submission to the SP 2 The number of required nodes and the job time are indicated in the above script 6 1 2 5 select select is a macro enabling easy selection of one of the test cases It invokes the unix commands cp data TEST 1 CONTROL CONTROL cp data TEST 1 FIELD FIELD cp data TEST 1 CONFIG CONFIG select requires one argument an integer to be specified sel
14. We also request that our users respect the integrity of DL POLY 2 source and not pass it on to third parties We require that all users of the package register with us not least because we need to keep everyone abreast of new developments and discovered bugs We have developed various forms of licence which we hope will ward off litigation from both sides without denying CCLRC 12 access to genuine scientific users In the next section we outline the capabilities of DL_POLY_2 as briefly as possible This is followed by a description of the DL_POLY_2 directory structure and how to obtain the source code from Daresbury Laboratory Much more information is to be found later in this manual Access to all this information and more can be gained via out WWW page http www dl ac uk TCSC Software DL_POLY main html 1 2 Functionality The following is a list of the features DL_POLY_2 It is worth reminding users that DL_POLY_2 represents a package rather than a single program so users should consider piecing together their own program with the desired functionality We will however supply a consolidated program in the distributed source 1 2 1 Molecular Systems DL_POLY_2 will simulate the following molecular species 1 Simple atomic systems and mixtures e g Ne Ar Kr etc 2 Simple unpolarisable point ions e g NaCl KCl etc Polarisable point ions and molecules e g MgO H20 etc D ey C2 Simple rigid molecules e g CCl4 SF
15. and the routine EXCLUDE which identifies atoms that are explictly chemically bonded through bonds constraints or valence angles The resulting list is known as the excluded atoms list The calculation of the pair forces represents the bulk of any simulation A Verlet neighbour list is used by DL POLY 2 in calculating the atomic forces The routine that constructs this this is called PARLST This routine builds the neighbour list taking into account the occurrence of atoms in the excluded atoms list The routine SRFRCE calculates the short range van der Waals forces making use of the IMAGES routine to handle any periodic boundary conditions Coulombic forces are handled by a varity of routines COULO COUL1 and COUL2 handle Coulombic forces without periodic boundaries EWALD1 EWALD2 and EWALD3 are used for systems with periodic boundaries an additional routine EWALD4 is necessary for the multiple timestep algorithm Intramolecular forces require the routines ANGFRC BNDFRC and DIHFRC If the multiple timestep algorithm is required the routine MULTIPLE must be used to call the various forces routines It also calls the PRIMLST routine to split the interaction list into primary and secondary neighbours The decision to update the neighbour list is handled by the routine VERTEST The routine EXTNFLD is required if the simulated system has an external force field e g electrostatic field operating To help with equilibration simulations the routine
16. found in the source directory of DL_POLY_2 section 7 1 1 Changing ndump necessitates recompiling DL POLY 2 REVCON is identical in format to the CONFIG input file see section 4 1 2 REVCON should be renamed CONFIG to continue a simulation from one job to the next This is done for you by the copy macro supplied in the execute directory of DL POLY 2 4 2 4 The REVIVE File This file is unformatted and written by the subroutine REVIVE It contains the accumulated statistical data It is updated whenever the file REVCON is updated see previous section REVIVE should be renamed REVOLD to continue a simulation from one job to the next This is done by the copy macro supplied in the execute directory of DL POLY 2 In addition to continue a simulation from a previous job the restart keyword must be included in the CONTROL file The format of the REVIVE file is identical to the REVOLD file described in section 4 1 4 4 2 5 The RDFDAT File This is a formatted file containing em Radial Distribution Function RDF data Its con tents are as follows record 1 cfgname character A80 configuration name record 2 ntpvdw integer 110 number of RDFs in file CCLRC 132 mxrdf integer 110 number of data points in each RDF There follow the data for each individual RDF i e ntpvdw times The data supplied are as follows first record atname 1 character A8 first atom name atname 2 character A8 second atom name following reco
17. inadvertently to over constrain a molecule e g by defining a methane tetrahedron to have 10 rather than 9 bond constraints in which case the SHAKE procedure will become unstable In addition massless sites e g charge sites cannot be included in a simple constraint approach making modelling with potentials such as TIP4P water impossible All these problems may be circumvented by defining rigid body units in terms of a center of mass c o m and an orientation and solving the resultant rigid body equations of motion A rigid body has associated with it a rotational inertia matrix I whose components are given by Zag 1 2 sitos Marg Where the r are the distance to the centre of mass and the m are the site masses In DL_POLY_2 we define the local body frame to be that in which the rotational inertia tensor i is diagonal and the components satisfy Iz gt Ij gt Izz These three components are stored in the arrays rotinx rotiny and rotinz for each unique type of rigid body in the system The total mass of the rigid body unit M is stored in the array gmass and the location of sites with respect to the local body axes are stored in the arrays gxx gyy and gzz The orientation of a local body frame with respect to the space fixed frame is described via a four dimensional unit vector the quaternion q go q1 92 q3 The Rotational matrix to transform from the local body frame to the space fixed frame is the unitary matrix a a g a 2 q1q
18. number will cure the problem but you can try follow standard user response to increase the parameter mxshak But the trouble is much more likely to be cured by careful consideration of the physical system being simulated For example is the system stressed in some way Too far from equilibrium Message 440 error undefined angular potential A form of angular potential has been requested which DL_POLY_2 does not recognise Action Locate the offending potential in the FIELD file and remove Replace with one acceptable to DL_POLY_2 if this is possible Alternatively you may consider defining the required potential in the code yourself Amendments to subroutines SYSDEF and ANGFRC will be required Message 442 error undefined three body potential A form of three body potential has been requested which DL POLY 2 does not recognise Action Locate the offending potential in the FIELD file and remove Replace with one acceptable to DL POLY 2 if this is reasonable Alternatively you may consider defining the required CCLRC 209 potential in the code yourself Amendments to subroutines SYSDEF and THBFRC will be required Message 443 error undefined four body potential DL_POLY_2 has been requested to process a four body potential it does not recognise Action Check the FIELD file and make sure the keyword is correctly defined Make sure that subroutine FBPFRC contains the code necessary to deal with the requested potential Add
19. the overall statistics The directive delr specifies the width of the border to be used in the Verlet neighbour list construction The width is stored in the variable delr The list is updated whenever two or more atoms have moved a distance of more then delr 2 from their positions at the last update of the Verlet list Users are advised to study the example CONTROL files appearing in the data sub directory to see how different files are constructed CCLRC 106 Table 4 1 Internal Restart Key start new simulation from CONFIG file and assign velocities from Gaussian distribution continue current simulation start new simulation from CONFIG file and rescale velocities to desired temperature Table 4 2 Internal Ensemble Key Microcanonical ensemble NVE Evans NVT ensemble Berendsen NVT ensemble Nos Hoover NVT ensemble Berendsen NPT ensemble Nos Hoover NPT ensemble Berendsen NoT ensemble Nos Hoover No T ensemble Potential of mean force NVE ensemble ON Oo hWN FH Table 4 3 Internal Trajectory File Key coordinates only in file coordinates and velocities in file coordinates velocities and forces in file Table 4 4 Non bonded force key meaning odd evaluate short range potentials and electrostatics Electrostatics are evaluated as follows Ignore Electrostatic interactions Ewald summation distance dependent dielectric constant standard truncated Coulombic potential truncated and shif
20. v t an w t sat At I x 1 n 70 E E lut AD olt 740 N bo r t At r t At ut SAU at At EC SAU Eo Ir 4 r t At 2 178 N 1 r t At where 1 is the identity matrix and g the pressure tensor The new cell vectors are calculated from H r Ai H t exp At qt 500 2 179 DL_POLY_2 uses a power series expansion truncated at the quadratic term to approximate the exponential of the tensorial term The new volume is found from V At V t exp At tr n 2 180 The conserved quantity is 3N kBText Jiu Pr Huvr PextV t 2 tr o t 7 2 181 This algorithm is implemented in the routines NST H nonbonded systems and NPT_H3 with bond constraints CCLRC 65 2 5 5 2 Berendsen Barostat With the Berendsen barostat the system is made to obey the equation of motion dP P L Pas P TP 2 182 Cell size variations In the isotropic implementation at each step the MD cell volume is scaled by by a factor 7 and the coordinates and cell vectors by 7 3 where At 7 1 P Pe P 2 183 TP and is the isothermal compressibility of the system The Berendesen thermostat is applied at the same time In practice is a specified constant which DL POLY 2 takes to be the isothermal compressibility of liquid water The exact value is not critical to the algorithm as it relies on the ratio 7p f Tp is specified by the user This al
21. x coordinate y coordinate z coordinate x component of velocity y component of velocity z component of velocity x component of force y component of force z component of force Thus the data for each atom is a minimum of two records and a maximum of 4 4 2 1 2 The Unformatted HISTORY File The unformatted HISTORY file is written by the subroutine TRAJECT U and has the fol lowing structure CCLRC 127 record 1 header configuration name character 80 record 2 natms number of atoms in the configuration real 8 record 3 atname 1 natms atom names or symbols character 8 record 4 weight 1 natms atomic masses real 8 record 5 charge 1 natms atomic charges real 8 For time steps greater than nstraj the HISTORY file is appended at intervals specified by the traj directive in the CONTROL file with the following information record i nstep the current time step real 8 natms number of atoms in configuration real 8 keytrj trajectory key real 8 imcon image convention key real 8 tstep integration timestep real 8 record ii for imcon gt 0 cell 1 9 a b and c cell vectors real 8 record iii xxx 1 natms atomic x coordinates real 8 record iv yyy 1 natms atomic y coordinates real 8 record v zzz 1 natms atomic z coordinates real 8 record vi only for keytrj gt 0 vxx 1 natms atomic velocities x component real 8 record vii only for keytrj gt 0 vyy 1 nat
22. 2 42 i l However it is possible to show by tedious algebra using the above formulae or more elegantly by thermodynamic arguments 26 that the dihedral makes no contribution to the atomic virial The contribution to be added to the atomic stress tensor is given by gm A rep TA rei 2 43 cos hyip m n n reg rd ro n rene with pi r Ti LjkLynla Tents gla 12a x Tikli jk x Ten 2 44 Pn a r RES kla z TE jkla dios xr Hel ak x Beal 2 45 Pik rijlLirErnlo atta 2r5plLijL enla l Liz X rjkllrjk X Lenl 2 46 gi ry Lia jkla ure la Me x Tj A 2 47 gk Ar o r rijtjklo Iri x rj 2 48 h moin dac Ten outs lols Egg ER 2 49 hy Arrallimiinlo njkltiktkn o IE jk X Len 2 50 The sum of the diagonal elements of the stress tensor is zero since the virial is zero and the matrix is symmetric Lastly it should be noted that the above description does not take into account the possible inclusion of distance dependent 1 4 interactions as permitted by some force fields Such interactions are permissible in DL POLY 2 and are described in the section on pair potentials below DL POLY 2 also permits scaling of the 1 4 interactions by a numerical factor 1 4 interactions do of course contribute to the atomic virial In DL POLY 2 dihedral forces are handled by the routine DIHFRC OCCLRC 35 2 2 6 Improper Dihedral Angle Potentials Improper dihedrals are used to restrict the geo
23. 3 The makefile is executed with the appropriate keywords section 3 2 1 which select for specific computers and if a parallel machine is used the appropriate communication software 4 The makefile produces the executable version of the code which as a default will be named DLPOLY X and located in the execute subdirectory 5 To run the executable for the first time you require the files CONTROL FIELD and CONFIG and possibly TABLE if you have tabulated potentials These must be present in the directory from which the program is executed See section 4 1 for the description of the input files 6 Executing the program will produce the files OUTPUT REVCON and REVIVE and optionally STATIS HISTORY RDFDAT and ZDNDAT in the executing directory See section 4 2 for the description of the output files This simple procedure is enough to create a standard version to run the supplied test cases For versions preceeding 2 11 it will not run the larger benchmark cases however Creating a larger executable or one which is tailored to an application different from the test cases is more complicated The main difficulty centres on assigning appropriate array dimensions to meet the application s needs In versions of DL POLY 2 after 2 11 these dimensions are calculated by the subroutine PARSET F and its support routines CFGSCAN F CONSCAN F and FLDSCAN F These support routines scan the CONFIG CONTROL and FIELD files at the start of a run an
24. Action Standard user response Fix the parameter msbad Message 420 error bond vector work arrays too small in tethfrc The work arrays in TETHFRC have been exceeded Action Standard user response Fix the parameter msbad CCLRC 206 Message 421 error bond vector work arrays too small in dihfre The work arrays in DIHFRC have been exceeded Action Standard user response Fix the parameter msbad Message 422 error all pairs must use multiple timestep In DL_POLY_2 the all pairs option must be used in conjunction with the multiple timestep Action Activate the multiple timestep option in the CONTROL file and resubmit Message 423 error bond vector work arrays too small in shlfre The dimensions of the interatomic distance vectors have been exceeded in subroutine SHL FRC Action Standard user response Fix the parameter msbad Set equal to the value of the parameter mxshl Message 424 error electrostatics incorrect for all pairs When using the all pairs option in conjunction with electrostatic forces the electrostatics must be handled with either the standard Coulomb sum or with the distance dependent dielectric Action Rerun the simulation with the appropriate electrostatic option Message 425 error transfer buffer array too small in shlmerge The buffer used to transfer data between nodes in the subroutine SHLMERGE has been di mensioned too small Action Standard user response Fi
25. Lewis Whitehead at the University of Southampton 5 1 2 8 Benchmark 8 Simulation of an isolated magnesium oxide microcrystal comprised of 5416 atoms originally in the shape of a truncated octahedron Uses full coulombic potential Runs on 16 512 processors 5 1 2 9 Benchmark 9 Simulation of a model membrane with 196 41 unit membrane chains 8 valinomycin molecules and 3144 water molecules using an adapted AMBER potential multiple timestep algorithm and Ewald sum electrostatics The system is comprised of 18866 atoms and runs on 8 512 processors Chapter 6 DL_POLY_2 Utilities 144 CCLRC 145 Scope of Chapter This chapter describes the more important utility programs and subroutines of DL_POLY_2 found in the sub directory utility A more complete description of the sub directory contents is to be found in the DL_POLY_2 Reference Manual 6 1 Miscellaneous Utilities 6 1 1 PARSET 6 1 1 1 Header records program parset C Ck ada ale ade ok ok ok ok ok ok ade ade ok ok ok ale ok ok ok ok ale ok ok ok ok ok ale ole ok ok ok ok ok ok ok ade ade ok ok ok ok ok ale ok ok ok ok ok ale ale ok ok ok ok ale ok ok ade ad ok ale oke ok ok ale ale ok a 2k ale dl poly utility program to prepare the dl params inc file for specific dl poly applications author w smith t forester jan 1995 copyright daresbury laboratory 1995 000000 O0 Ck ada ale ade ok ok ok ok ok ok ade ade ok ok ok ale ok ok ok ok ale ok ok ok ok ok ale ok o
26. T P Hoover 16 with FIQA and RD SHAKE NPTQ H2 Constant T P Hoover 16 with QSHAKE NPTQ H3 Constant T c Hoover 16 with FIQA and RD SHAKE NPTQ H4 Constant T g Hoover 16 with QSHAKE Lond In the above table the FIQA algorithm is Fincham s Implicit Quaternion Algorithm 12 and QSHAKE is the DL POLY 2 algorithm combining rigid bonds and rigid bodies in the same molecule 13 2 5 1 Bond Constraints The SHAKE algorithm for bond constraints was devised by Ryckaert et al 11 and is widely used in molecular simulation It is a two stage algorithm based on the Verlet integration scheme 10 DL POLY 2 employs a leapfrog variant In the first stage the Verlet leapfrog algorithm calculates the motion of the atoms in the system assuming a complete absence of the rigid bond forces The positions of the atoms at the end of this stage do not conserve the distance constraint required by the rigid bond and a correction is necessary In the second stage the deviation in the length of a given rigid bond is used retrospectively to compute the constraint force needed to conserve the bondlength It is relatively simple to CCLRC 58 show that the constraint force has the form _ big di dis where uij is the reduced mass of the two atoms connected by the bond dij and dij are the original and intermediate bond vectors dij is the constrained bondlength and At is the Verlet integration time step It should be noted that this for
27. The value of nummols for this molecule determines the number of pmf constraint in the system 8 angles n where n is the number of valence angle bonds in the molecule Each of the n records following contains angle key ad potential key See table 4 8 index 1 integer first atomic index CCLRC 116 index 2 integer second atomic index central site index 3 integer third atomic index variable 1 real potential parameter see table 4 8 variable 2 real potential parameter see table 4 8 The meaning of these variables is given in table 4 8 See the note on the atomic indices appearing under the shell directive above This directive and associated data records need not be specified if the molecule contains no angular terms Table 4 8 Valence Angle potentials potential type Variables 1 4 functional formt Harmonic U 0 8 69 Quartic U 0 0 09 E 8 69 amp 0 69 Truncated harmonic U 8 E 0 69 exp r2 tr15 05 Screened harmonic U 0 E 0 00 exp rij p1 riz p2 Screened Vessal 24 U 0 SU o r 0 m1 exp rij p1 Tip p2 Truncated Vessal 25 U 0 k 0 0 09 0 4 69 21 Er 8 69 x 69 exp r5 rik 9 Harmonic Cosine U 0 cos 0 cos 6o Cosine U 0 A 1 cos m 10 is the a b c angle Note valence angle potentials with a dash as the first character of the keyword do not cont
28. algorithm 41 which is generally a system specific utility CCLRC 76 Similarly the total configuration energy and virial must be obtained as a global sum of the contributing terms calculated on all nodes 2 6 8 The RD SHAKE and Parallel QSHAKE Algorithms The RD SHAKE algorithm is a parallel adaptation of SHAKE couched in the Replicated Data strategy The essentials of the RD SHAKE method are as follows 1 The bond constraints acting in the simulated system are shared equally between the processing nodes 2 Each node makes a list recording which atoms are bonded by constraints it is to process Entries are zero if the atom is not bonded 3 A copy of the array is passed to each other node in turn The receiving node compares the incoming list with its own and keeps a record of the shared atoms and the nodes which share them 4 In the first stage of the SHAKE algorithm the atoms are updated through the usual Verlet algorithm without regard to the bond constraints 5 In the second iterative stage of SHAKE each node calculates the incremental cor rection vectors for the bonded atoms in its own list of bond constraints It then sends specific correction vectors to all neighbours that share the same atoms using the information compiled in step 3 6 When all necessary correction vectors have been received and added the positions of the constrained atoms are corrected 7 Steps 5 and 6 are repeated until the bond constrai
29. and REVCON sections 4 2 4 and CCLRC 83 4 2 3 respectively An idea of the construction of a DL_POLY_2 program can be obtained from the following flowchart The example represents a DL_POLY_2 program which uses the multiple timestep algorithm with bond constraints and the Nos Hoover thermostat CCLRC DLPOLY MACHINE SYSDEF SYSGEN VERTEST PARLST MULTIPLE BNDFRC ANGFRC DIHFRC EXTNFLD GDSUM FORCES FCAP NVT H1 VSCALE STATIC REVIVE TRAJECT RESULT EXCLUDE INTLIST QUENCH VSCALE LRCORRECT EWALD1 PRIMLST SRFRCE EWALD2 4 COULO 1 or 2 EWALD3 REVIVE 84 PASSCON SHMOVE SPLICE SHMOVE SPLICE CCLRC 85 3 2 Compiling and Running DL POLY 2 3 2 1 Compiling the Source Code When you have obtained DL_POLY_2 from Daresbury Laboratory and unpacked it your next task will be to compile it To aid compilation a general makefile Makefile has been provided in the sub directory build see Appendix A to this document The general DL_POLY_2 makefile will build an executable with a wide range of functionality sufficient for the test cases and for most users requirements Other makefiles are found in the build sub directory for variants of DL_POLY_2 such as the respa version Users will need to modify the makefile if they are to add additional functionality to the code or if it requires adaptation for a non specified computer Modifications may a
30. and the directive timesteps adjusted in the CONTROL file to the new total number of steps required for the simulation For example if you wish to extend a 10000 step simulation by a further 5000 steps use the directive timesteps 15000 in the CONTROL file and include the restart directive You can use the restart scale directive if you want to reset the temperature at the restart but note that this also resets all internal accumulators timestep included to zero 3 3 A Guide to Preparing Input Files The CONFIG file and the FIELD file can be quite large and unwieldy particularly if a polymer or biological molecule is involved in the simulation This section outlines the paths to follow when trying to construct files for such systems The description of the DL POLY 2 force field in chapter 2 is essential reading The various utility routines mentioned in this section are described in greater detail in chapter 6 Many of these have been incorporated into the DL POLY 2 Graphical User Interface 20 and may be convenently used from there CCLRC 92 3 3 1 Inorganic Materials The utility GENLAT can be used to construct the CONFIG file for relatively simple lattice structures Input is interactive The FIELD file for such systems are normally small and can be constructed by hand The utility GENLAT TO constructs the CONFIG file for truncated octahedral boundary conditions Otherwise the input of force field data for crystalline systems is particular
31. array too small in parlst Construction of the Verlet neighbour list in subroutine parlst nonbonded pair force has exceeded the neighbour list array dimensions Action Standard user response Fix the parameter mxlist Message 112 error vertest array too small This error results when the dimension of the DL_POLY_2 VERTEST arrays which are used in checking if the Verlet list needs updating have been exceeded Action Standard user response Fix the parameter mslst Message 120 error invalid determinant in matrix inversion DL_POLY_2 occasionally needs to calculate matrix inverses usually the inverse of the ma trix of cell vectors which is of size 3 x 3 For safety s sake a check on the determinant is made to prevent inadvertent use of a singular matrix Action Locate the incorrect matrix and fix it e g are cell vectors correct Message 130 error incorrect octahedral boundary condition When calculating minimum images DL_POLY_2 checks that the periodic boundary of the simulation cell is compatible with the specifed minimum image algorithm Program termi nation results if an inconsistency is found In this case the error refers to the truncated CCLRC 195 octahedral minimum image which is inconsistent with the simulation cell The most prob able cause is the incorrect definition of the simulation cell vectors present in the input file CONFIG these must equal the vectors of the enscribing cubic cell A
32. arrays in subroutine FORCESNEU is too small Action Standard user response Fix the parameter mxxdf Message 479 error mxxdf too small in multipleneu subroutine The parameter mxxdf defining working arrays in subroutine MULTIPLENEU is too small Action Standard user response Fix the parameter mxxdf Message 484 error only one potential of mean force permitted It is not permitted to define more than one potential of mean force in the FIELD file Action Check that the FIELD file contains only one PMF specification If more than one is needed DL_POLY_2 cannot handle it CCLRC 214 Message 490 error PMF parameter mxpmf too small in passpmf The bookkeeping arrays have been exceeded in PASSPMF Action Standard user response Fix the parameter mxpmf Set equal to mxatms Message 492 error parameter mxcons lt number of PMF constraints The parameter mxcons is too small for the number of PMF constraints in the system Action Standard user response Fix the value of mxcons Message 494 error in csend pvmfinitsend The PVM routine PVMFINITSEND has returned an error It is invoked by the routine CSEND Action Check your system implementation of PVM Message 496 error in csend pvmfpack The PVM routine PVMFPACK has returned an error It is invoked by the routine CSEND Action Check your system implementation of PVM Message 498 error in csend pvmfsend The PVM routine PVMFSEND has returned an erro
33. boundaries These are describe in detail in Appendix B 1 2 4 Algorithms 1 2 4 1 Parallel Algorithms DL POLY 2 exclusively employs the Replicated Data parallelisation strategy 8 9 CCLRC 14 1 2 4 2 Molecular Dynamics Algorithms The DL_POLY_2 MD algorithms are all couched in the form of the Verlet Leapfrog integra tion algorithm 10 NVE NVT NPT and NoT ensembles are available with a selection of thermostats and barostats A parallel version of the SHAKE algorithm 11 called RD SHAKE is used for bond constraints 9 Fincham s implicit quaternion algorithm FIQA 12 is available for rigid molecular species Rigid molecular species linked by rigid bonds are handled with an algorithm of our own devising called the QSHAKE algorithm 13 The following MD algorithms are available 1 Verlet leapfrog 2 Verlet leapfrog with RD SHAKE 3 Rigid molecules with FIQA and RD SHAKE 4 Linked rigid molecules with QSHAKE 13 5 Berendsen constant T algorithm with Verlet or RD SHAKE 14 6 Evans constant T algorithm with Verlet or RD SHAKE 15 7 Hoover constant T algorithm with Verlet or RD SHAKE 16 8 Berendsen constant T algorithm with FIQA and RD SHAKE 14 9 Berendsen constant T algorithm with QSHAKE 14 10 Hoover constant T algorithm with FIQA and RD SHAKE 16 11 Hoover constant T algorithm with QSHAKE 16 12 Berendsen constant T P algorithm with RD SHAKE 14 13 Berendsen constant T g algorithm with R
34. dt pos at oi de cde t ee ed The Intermolecular Potential Functions ccn 2 3 1 2 3 2 2 3 3 2 3 4 2 3 5 Short Ranged van der Waals Potentials Metal Potentials 1 a Sie ER Ba es rado Three Body Potentials e Four Body Potentials o lees External Eield8 ms a de AT EE ES Long Ranged Electrostatic Coulombic Potentials 2 4 1 2 4 2 2 4 3 2 4 4 2 4 5 2 4 6 2 4 7 2 4 8 Atomistic and Charge Group Implementation Direct Coulomb SUM Truncated and Shifted Coulomb Sum Coulomb Sum with Distance Dependent Dielectric Ewald Sumi sei e a eos SMa a S RARUS ula Smooth Particle Mesh Ewald 0 o Reaction Field 34 4 xd a e a Dynamical Shell Model cens Integration algorithms le 2 5 1 2 5 2 2 5 3 2 5 4 2 5 5 2 5 6 2 5 7 2 5 8 Bond Constraints 22r s Potential of Mean Force PMF Constraints and the Evaluation of Free METE Y drid E as dae YE Oe e eds T h rinostats iniu i een Eee ege E ELY Vara Be ed Gaussian Constraints iaa D ce Che et CHR o ene e x Barostats woes dor A ee retire A e Rigid Bodies and Rotational Integration Algorithms The DL_POLY_2 Multiple Timestep Algorithm The DL_POLY_2 RESPA Multiple Timestep Implementation DL_POLY Parallelisation rh 2 6 1 2 6 2 2 6 3 2 6 4 2 6 5 2 6 6 The Replica
35. giving CCLRC 17 1 The name of the author and or modifying author 2 The version number or date of production 3 A brief description of the function of the subroutine 4 A copyright statement 5 A CVS revision number and associated data Elsewhere FORTRAN COMMENT cards are used liberally 1 3 8 Subroutine Function Calling Sequences The variables in the subroutine arguments are specified in the order 1 logical and logical arrays 2 character and character arrays 3 integer 4 real and complex 5 integer arrays 6 real and complex arrays This is admittedly arbitrary but it really does help with error detection 1 3 9 FORTRAN Parameters All parameters defined by the FORTRAN parameter statements are specified in the include file DL_PARAMS INC which is included at compilation time in all subroutines requiring the parameters All parameters specified in DL_PARAMS INC are described by one or more comment cards Note that since the implementation of FORTRAN 90 memory management in Version 2 11 the DL_PARAMS INC file also contains the COMMON block params described above 1 3 10 Arithmetic Precision All real variables and parameters are specified in 64 bit precision i e real 8 CCLRC 18 1 3 11 Units Internally all DL_POLY_2 subroutines and functions assume the use of the following defined molecular units 1 The unit of time to is 1 x 1071 seconds i e picoseconds 2 The unit of length o is 1 x
36. i 2 147 4reg This expression unfortunately leads to large fluctuations in the system Coulombic energy due to the large step in the function at the cavity boundary In DL_POLY_2 this is countered by subtracting the value of the potential at the cavity boundary from each pair contribution The term subtracted is l gjgn T 1 2 148 4neg Re 2 The effective pair force on an atom j arising from another atom n within the cavity is given by djd 1 Bo aI nj 2 149 j Are E 21 cM The contribution of each effective pair interaction to the atomic virial is and the contribution to the atomic stress tensor is gu cq 2 151 In DL POLY 2 the reaction field is handled by the routines COUL3 and COUL3NEU 2 4 8 Dynamical Shell Model An atom or ion is polarisable if it develops a dipole moment when placed in an electric field It is commonly expressed by the equation w aE 2 152 where y is the induced dipole and E is the electric field The constant o is the polarisability CCLRC 55 The dynamical shell model is a method of incorporating polarisability into a molecular dynamics simulation The method used in DL_POLY_2 is that devised by Fincham et al 33 and is known as the adiabatic shell model An alternative model is presented in 34 In the static shell model a polarisable atom is represented by a massive core and massless shell connected by a harmonic spring hereafter called the core shel
37. ifrz gt 0 igrp integer neutral charge group number The integer nrept need not be specified in which case a value of 1 is assumed A number greater than 1 specified here indicates that the next nrept 1 entries in the CONFIG file are ascribed the atomic characteristics given in the current record The sum of the repeat numbers for all atoms in a molecule should equal the number specified by the atoms directive 4 shell n where n is the number of core shell units Each of the subsequent n records contains index 1 integer site index of core index 2 integer site index of shell spring real force constant of core shell spring The spring force constant is entered in units of engunit A where engunit is the energy unit specified in the units directive Note that the atomic site indices referred to in this table are indices arising from numbering each atom in the molecule from 1 to the number specified in the atoms directive for this molecule This same numbering scheme should be used for all de scriptions of this molecule including the bonds constraints angles and dihe drals entries described below DL_POLY_2 will itself construct the global indices for all atoms in the systems This directive and associated data records need not be specified if the molecule contains no core shell units 5 bonds n where n is the number of flexible chemical bonds in the molecule Each of the subse quent n records contains CCLRC 114 bon
38. intramolecular force field It does not then expect to encounter directives not related to these data This error message results if it encounters a unrelated directive The most probable cause is incomplete specification of the data e g when the finish directive has been omitted Action Check the molecular data entries in the FIELD file and correct Message 13 error molecule species not specified This error arises when DL_POLY_2 encounters non bonded force data in the FIELD file before the molecular species have been specified Under these circumstances it cannot as sign the data correctly and therefore terminates Action Make sure the molecular data appears before the non bonded forces data in the FIELD file and resubmit CCLRC 180 Message 14 error too many unique atom types specified This error arises when DL_POLY_2 scans the FIELD file and discovers that there are too many different types of atoms in the system i e the number of unique atom types exceeds the mxsvdw parameter Action Standard user response Fix parameter mxsvdw Message 15 error duplicate pair potential specified In processing the FIELD file DL_POLY_2 keeps a record of the specified short range pair potentials as they are read in If it detects that a given pair potential has been specified before no attempt at a resolution of the ambiguity is made and this error message results See specification of FIELD file Action Locate the d
39. m position The torque acting upon the body in the space fixed frame is r Yd xf 2 191 Transformed to the local body frame and including the centrifugal terms this is f R r eta 2 192 where Ma Doy 1 z2 9yGz 2 193 plus cyclic permutations for y and z components The angular velocity transformed to the local body frame w can then be integrated using the leapfrog algorithm and the diagonal rotational inertia tensor At At an amp t 0 t E Ati 20 2 194 The new quaternions cannot be found so simply DL_POLY_2 uses Fincham s implicit quaternion algorithm FIQA to do this 12 In this algorithm the new quaternions are found by solving the implicit equation g t At q t A Quela Qla Ata t At 2 195 where 0 6 and Qla is qdo Q 42 43 liq 4o 8 q2 en 2 196 Q 2i B qo q 93 432 q qo The above equation is solved iteratively with q t At q t At Qla t w t 2 197 as the first guess Typically no more than 3 or 4 iterations are needed for convergence At each step the constraint la t At 2 1 2 198 is imposed The quaternions are stored in the arrays q0 qi q2 and q3 The angular velocity transformed to the body fixed frame is stored in the arrays omx omy and omx while CCLRC 68 the work arrays opx opy opz oqx ogy oqz hold values of t and w t At The torques 7 t are held in the work arrays tqx tay and taz The NV
40. molecules are treated as rigid bodies The TAB headgroup has fractional charges summing to 1 the bromide ion has charge 1 The Ewald sum handles the electrostatic calculations The short range forces are taken from the Dreiding force field 5 1 1 10 Test Case 10 DNA strand in water This system consists of a strand of DNA 1260 atoms in length in a solution of 706 SPC water molecules The DNA is aligned in the Z direction and hexagonal prism periodic boundary conditions applied The electrostatic interactions are calculated using the Smooth Particle Mesh Ewald method Note that the system has a strong overall negative charge which is strongly anisotropic in distribution The short range forces are taken from the Dreiding force field and constraints are used for all covalent bonds For simplicity H bonds are treated as harmonic bonds with an equilibrium bondlength of 1 724 A CCLRC 142 5 1 2 Benchmark Cases These represent rather larger test cases for DL_POLY_2 that are also suitable for bench marking the code on large scale computers They have been selected to show fairly the the capabilities and limitations of the code 5 1 2 1 Benchmark 1 Simulation of metallic aluminium at 300K using a Sutton Chen density dependent potential The system is comprised of 19652 identical atoms The simulation runs on 16 to 512 processors only 5 1 2 2 Benchmark 2 Simulation of a 15 peptide in 1247 water molecules This was designed as an AMBE
41. mxexcl exceeded in excludeneu routine An error has been detected in the construction of the excluded atoms list for neutral groups This occurs when the parameter mxexcl is exceeded in the EXCLUDENEU routine Action Standard user response Fix parameter mxexcl CCLRC 199 Message 300 error incorrect boundary condition in parlink The use of link cells in DL_POLY_2 implies the use of appropriate boundary conditions This error results if the user specifies octahedral dodecahedral or slab boundary conditions Action The simulation must be run with cubic orthorhombic or parallelepiped boundary condi tions Message 301 error too many rigid body types The maximum number of rigid body types permitted by DL POLY_2 has been exceeded Action Standard user response Fix the parameter mxungp Message 302 error too many sites in rigid body This error arises when DL_POLY_2 finds that the number of sites in a rigid body exceeds the dimensions of the approriate storage arrays Action Standard user response Fix the parameter mxngp Message 303 error too many rigid bodies specified The maximum number of rigid bodies in a simulation has been reached Do not confuse this with message 304 below Action Standard user response Fix the parameter mxgrp Message 304 error too many rigid body sites in system This error occurs when the total number of sites within all rigid bodies exceeds the permit ted maximum Do
42. mxshak You may also consider reducing the tolerance of the SHAKE iteration the directive shake in the CONTROL file However it is probably better to take a good look at the starting conditions Message 71 error too many metal potentials specified The number of metal potentials that can be specfied in the FIELD file is limited This error results if too many are used Action Standard user response Fix the parameter mxvdw Note that this parameter must be double the number of required metal potentials Recompile the program Message 73 error too many inversion potentials specified The number of inversion potentials specified in the FIELD file exceeds the permitted max imum Action Standard user response Fix the parameter mxtinv Message 75 error too many atoms in specified system DL_POLY_2 places a limit on the number of atoms that can be simulated Termination results if too many are specified Action Standard user response Fix the parameter mxatms Message 77 error too many inversion potentials in system The simulation contains too many inversion potentials overall causing termination of run Action Standard user response Fix the parameter mxinv CCLRC 189 Message 79 error incorrect boundary condition in fbpfrc The 4 body force routine assumes a cubic or parallelepiped periodic boundary condition is in operation The job will terminate if this is not adhered to Action You must reconf
43. routines described in chapter 7 of the DL POLY 2 Reference Manual for further details particularly regarding further dependencies i e additional routines that must be called The following outline assumes a system containing flexible molecules held together by rigid bonds but without rigid bodies Initialisation requires firstly that the program determine what kind of parallel machine it is running on The routine MACHINE determines how many processing nodes are being used and also returns the node identity to each process Next the job control information is required this is obtained by the routine SIMDEF which reads the CONTROL file section CCLRC 82 4 1 1 The description of the system to be simulated the types of atoms and molecules present and the intermolecular forces are obtained by the SYSDEF routine which reads the FIELD file section 4 1 3 Lastly the atomic positions and velocities must be provided These are obtained by the SYSGEN routine which reads the CONFIG file section 4 1 2 and also generates the initial velocities if required to do so If the system contains con straint bonds the routine PASSCON is required to process molecular connectivity data and establish the communication procedure between nodes and the QUENCH routine is required to set the starting velocities correctly Also needed in the initialisation is the routine FOR GEN which constructs the interpolation arrays for the short range forces calculations
44. sensitive 4 1 3 2 Definitions of Variables The file divides into three sections general information molecular descriptions and non bonded interaction descriptions appearing in that order in the file 4 1 3 2 1 General information The first record in the FIELD file is the title It must be followed by the units directive Both of these are mandatory These records may optionally be followed by the neut directive record 1 header a80 field file header CCLRC 112 record 2 units a40 Unit of energy used for input and output record 3 optional neut a40 activate the neutral charge groups option for the electrostatic calculations The energy units on the units directive are described by additional keywords a eV for electron volts b kcal for k calories mol c kJ for k Joules mol d internal for DL POLY 2 internal units 10 J mol 1 If no units keyword is entered DL POLY 2 units are assumed for both input and output The units keyword may appear anywhere on the data record provided it does not exceed column 40 The units directive only affects the input and output interfaces all internal calculations are handled using DL POLY 2 units 4 1 3 2 2 Molecular details It is important for the user to understand that there is an organisational correspondence between the FIELD file and the CONFIG file described above It is required that the order of specification of molecular types and their atomic constituents i
45. shifting process Tabulation tab The potential is defined numerically only The parameters defining these potentials are supplied to DL POLY 2 at run time see the description of the FIELD file in section 4 1 3 Each atom type in the system is specified by a unique eight character label defined by the user The pair potential is then defined internally by the combination of two atom labels As well as the numerical parameters defining the potentials DL POLY 2 must also be provided with a cutoff radius rey which sets a range limit on the computation of the interaction Together with the parameters the cutoff is used by the subroutine FORGEN or FORGEN RSQ to construct an interpolation array vvv for the potential function over CCLRC 41 the range 0 to Tew A second array ggg is also calculated which is related to the potential via the formula 10 G rij rijg U rig 2 80 ij and is used in the calculation of the forces Both arrays are tabulated in units of energy The use of interpolation arrays rather than the explicit formulae makes the routines for calculating the potential energy and atomic forces very general and enables the use of user defined pair potential functions DL_POLY_2 also allows the user to read in the interpolation arrays directly from a file see the description of the FORTAB routine chapter 7 and the TABLE file section 4 1 5 This is particularly useful if the pair potential function has no si
46. specified cutoff for the van der Waals potentials If not specified its value defaults to rcut CCLRC 105 10 11 12 13 c rprim this is used in the multiple timestep algorithm to specify the primary atom region see section 2 5 7 It has no meaning if the multiple timestep option is not used Some directives are optional If not specified DL_POLY_2 will take default values if necessary The defaults appear in the above table The zero directive enables a zero temperature simulation This is intended as a crude energy minimizer to help relax a system before a simulation begins It should not be thought of as a true energy minimization method The DL_POLY_2 multiple timestep option is invoked if the number appearing with the mult directive is greater than 2 This number stored in the variable multt specifies the number of timesteps the multi step that elapse between partitions of the full Verlet neighbour list into primary and secondary atoms If a multiple time step is used i e multt gt 2 then statistics for radial distribution functions are collected only at updates of the secondary neighbour list The num ber specified on the rdf directive the variable nstbgr means that RDF data are accumulated at intervals of nstbgr xmultt timesteps As a default DL_POLY_2 does not store statistical data during the equilibration period If the directive collect is used equilibration data will be incorporated into
47. subtended by a triplet of atoms is maintained around some preset value 0o is handled as a special case of angle potentials As a consequence angle restraints may be applied only between atoms in the same molecule Unlike with application of the pure angle potentials the electrostatic and van der Waals interactions between the pair of atoms are stil evaluated when distance restraints are applied All the potential forms of the previous section are avaliable as angular restraints although they have different key words CCLRC 32 1 Harmonic hrm 2 Quartic qur 3 Truncated harmonic thm 4 Screened harmonic shm 5 Screened Vessal 24 bv1 6 Truncated Vessal 25 bv2 7 Harmonic cosine hes 8 Cosine cos 2 2 5 Dihedral Angle Potentials The dihedral angle and associated vectors The dihedral angle potentials describe the interaction arising from torsional forces in molecules They are sometimes referred to as torsion potentials They require the spec ification of four atomic positions The potential functions available in DL_POLY_2 are as follows 1 Cosine potential cos U dijkn A 1 cos Mpijrn 9 2 29 2 Harmonic harm 1 U pijen 5 tigen do 2 30 3 Harmonic cosine hcos U ijkn S cos diim cos do 2 31 CCLRC 33 4 Triple cosine cos3 U j t cos p IA cos 2p 5As 1 cos 3 2 32 In these formulae xn is
48. that simply increasing the iteration number will cure the problem but you can try follow the standard user response to increase the control parameter mxshak But the trouble is much more likely to be cured by careful consideration of the physical system being simulated For example is the system stressed in some way Too far from equilibrium Message 106 error neighbour list array too small in parlink Construction of the Verlet neighbour list in subroutine parlink nonbonded pair force has exceeded the neighbour list array dimensions Action Standard user response Fix the parameter mxlist Message 107 error neighbour list array too small in parlinkneu Construction of the Verlet neighbour list in subroutine parlinkneu nonbonded pair force has exceeded the neighbour list array dimensions Action Standard user response Fix the parameter mxlist CCLRC 194 Message 108 error neighbour list array too small in parneulst Construction of the Verlet neighbour list in subroutine parneulst nonbonded pair force has exceeded the neighbour list array dimensions Action Standard user response Fix the parameter mxlist Message 109 error neighbour list array too small in parlst_nsq Construction of the Verlet neighbour list in subroutine parlst_nsq nonbonded pair force has exceeded the neighbour list array dimensions Action Standard user response Fix the parameter mxlist Message 110 error neighbour list
49. the dihedral angle defined by Pijkn cos B r Tjj e 2 33 with i we Tij X Tjk jk X Ten B rij Tjj Lkn metas 2 34 eon leg x Pla X Tknl With this definition the sign of the dihedral angle is positive if the vector product rj x Tjk X Trjg X Tkn is in the same direction as the bond vector r and negative if in the opposite direction The force on an atom arising from the dihedral potential is given by o fe grg Piste 2 35 with being one of i j k n and q one of x y z This may be expanded into o 1 o o xc iign YT U hien B Tin T 2 36 are Pijkn la dijkn ijen are ata Lkn The derivative of the function B rj rjj T 4 is o 1 o 97g P Cir Lym Len x res x ns rg E T8 Eye n 2 37 ett I er vta with gra lEs X Cyn Lijk Lim rir ktjklo 0e Sen rjkTknlo 0ek ej roe C rijrjk o 0e Sek rjkTkn o 0c 4i Tn Irijrjklo 0ec Sej rjsrjk o 85 5ej ri rijT kno 0e Sex 2 38 Or Fit ral Wh lLynlinlaldr dei Ligtjnlac 5e Sen 2r lriLijlal m ej ritu o Se Sei 2 39 CCLRC 34 o are cma ttt X Len um aren yer jkla en See rjsrknlo 9ej 9n 2r 5k en knla Lx 965 rjstknlo 8ek 9e 2 40 Where we have used the the following definition la dla Y 1 ag a Vf 2 41 B Formally the contribution to be added to the atomic virial is given by 4 M ni f
50. the same direction and u is the fractional coordinate of ion j scaled by a factor K ie uj Ks5 Note that the definition of the B splines implies a dependence on the integer K which limits the formally infinite sum over L The coefficients M u are B splines of order n and the factor b k is a constant computable from the formula b k exp 2ri n 1 k K Mat lezp 2zik K 2 138 0 2 Approximation of the structure factor S k S k z b1 k1 b2 k2 b3 k3 Q k1 ko ka 2 139 OCCLRC 53 where Q1 k1 k2 k3 is the discrete Fourier transform of the charge array Q 1 2 3 defined as N Q A 42 43 Y q Y M uij amp ni Li Ms uj 45 n2D2 Mp us 43 n3L3 j 1 mimna na 2 140 in which the sums over n123 etc are required to capture contributions from all relevant periodic cell images which in practice means the nearest images 3 Approximating the reciprocal space energy Urecip 1 Urecip z5 gt G ki ko ks Q k1 ka k3 2 141 2Vo 0 ks in which Gt is the discrete Fourier transform of the function exp k 4a G ki ka k3 k2 B k1 ko ka Q Ki ko k3 2 142 and where B Ki ko k3 b1 Kx 7 b2 k2 7 bs ka 2 143 and Q Kk k2 k3 is the complex conjgate of Q k1 k2 k3 The function G k ka k3 is thus a relatively simple product of the gaussian screening term appearing in the conventional Ewald sum the function B k1 k2 k3
51. to find a temp directive in the CONTROL file CCLRC 202 Action Place a temp directive in the CONTROL file with the required temperature specified Message 381 error simulation timestep not specified DL_POLY_2 has failed to find a timestep directive in the CONTROL file Action Place a timestep directive in the CONTROL file with the required timestep specified Message 382 error simulation cutoff not specified DL POLY 2 has failed to find a cutoff directive in the CONTROL file Action Place a cutoff directive in the CONTROL file with the required forces cutoff specified Message 383 error simulation forces option not specified DL_POLY_2 has failed to find any directive specifying the electrostatic interactions options in the CONTROL file Action Ensure the CONTROL file contains at least one directive specifying the electrostatic po tentials e g ewald coul no electrostatics etc Message 384 error verlet strip width not specified DL_POLY_2 has failed to find the delr directive in the CONTROL file Action Insert a delr directive in the CONTROL file specifying the width of the verlet strip augmenting the forces cutoff Message 385 error primary cutoff not specified DL_POLY_2 has failed to find the prim directive in the CONTROL file Necessary only if multiple timestep option required Action Insert a prim directive in the CONTROL file specifying the primary cutoff radius in the multiple times
52. to the CCP5 directory cd ccp5 6 change to the DL POLY directory cd DL POLY 7 type binary 8 type get LICENCE ps Z 9 type quit The licence file will need to be uncompressed using the unix uncompress command before printing Note that there are two versions of the licence available one for single academic users with perhaps one or two postgraduate students and one for academic groups with perhaps several research staff including postdoctoral and permanent staff Choose the one most suitable for you Once you have obtained the licence form you should sign it and return it to the following address Dr W Smith DL POLY Program Library Computational Science and Engineering Department CCLRC Daresbury Laboratory Daresbury Warrington WA4 4AD England Please return the licenceby post please FAXes are not acceptable to our Contracts De partment When the signed licence has been received DL POLY 2 source code will be sent by ftp We will need to contact you about this procedure so please supply your e mail address Please note we cannot create accounts on any of our machines for this purpose CCLRC 22 The DL POLY 2 User Manual is freely available via World Wide Web or ftp in the same manner as the licence form The much larger DL POLY 2 Reference Manual will be available by the above ftp procedure only Daresbury Laboratory is the sole centre for the distribution of DL POLY 2 and copies obtained from elsewhere
53. variation in these variables follow on the next two lines The energy and pressure units are as for the preceeding section Also provided in this section is an estimate of the diffusion coefficient for the different species in the simulation which is determined from a single time origin and is therefore very approximate Accurate determinations of the diffusion coefficients can be obtained using the MSD utility program which processes the HISTORY file see chapter 6 If an NPT or Ng T simulation is performed the OUTPUT file also provides the mean stress pressure tensor and mean simulation cell vectors 4 2 2 7 Sample of Final Configuration The positions velocities and forces of the 20 atoms used for the sample of the initial configuration see above are given This is written by the subroutine RESULT 4 2 2 8 Radial Distribution Functions If both calculation and printing of radial distribution functions have been requested by selecting directives rdf and print rdf in the CONTROL file radial distribution functions are printed out This is written from the subroutine RDF1 First the number of time steps used for the collection of the histograms is stated Then each function is given in turn For each function a header line states the atom types a and b represented by the function Then r g r and n r are given in tabular form Output is given from 2 entries before the first non zero entry in the g r histogram n r is the a
54. was written on behalf of CCP5 2 in the eighteen months preceding September 1993 when the beta release appeared The principal authors at that stage were Bill Smith and Tim Forester at Daresbury Laboratory For want of a more imaginative acronym the package was named DL_POLY The entire DL_POLY project was given a major boost by the provision of a grant in January 1993 from the SERC s Computational Science Initiative An additional grant was made by the EPSRC in June 1994 to continue developments in the period 1995 97 In April 1995 the project came under the Council for the Central Laboratory of the Research Councils There were many reasons for writing the package The first reason being to exploit parallel computing for molecular simulation in the UK There were several worthy packages available to the academic community including GROMOS 3 AMBER 4 and X PLOR 5 but none of these were designed as far as we were able to tell with parallel computers in mind though parallel versions of these programs now exist We decided then that the effort involved in devising a new code which had parallelism built into it from the start would be well spent This we thought would allow us to adapt the code to new architectures with greater ease The second reason was to bring to fruition the high level of parallel programming expertise at Daresbury Laboratory and generally within the CCP5 community stretching back several years in the area of molecul
55. will be regarded as illegal and will not be supported 1 6 DLPROTEIN DLPROTEIN is a further development of DL POLY that was written by S Melchionna and S Cozzini with assistance from M Venturoli and Antonella Luise specifically to handle protein simulations In agreement with the authors the package is also available from Daresbury Laboratory under the same terms as DL POLY Though having much in common with DL POLY it represents a major rewrite with many features not present in the original code and with many original features missing It is therefore documented separately from DL POLY and users should consult the appropriate manual The DL PROTEIN User Manual by S Melchionna and S Cozzini 21 which also available from Daresbury Laboratory Our thanks go to S Melchionna and S Cozzini and their collaborators for generously making DLPROTEIN available to us and for extending that availablity to DL POLY 2 users 1 7 Other Information The DL POLY 2 web page http ftp dl ac uk TCS Software DL POLY main html pro vides additional information in the form of 1 Access to all documentation including licences 2 Frequently asked questions 3 Bug reports Daresbury Laboratory also maintains two DL_POLY_2 associated electronic mailing lists 1 dl_poly_news to which all registered DL POLY 2 users are automatically subscribed It is via this list that error reports and announcements of new versions are made If yo
56. you have chosen plus and minus 2096 Plot the Coulombic energy and W versus a If the Ewald sum is correctly converged you will see a plateau in the plot Divergence from the plateau at small o is due to non convergence in the real space sum Divergence form the plateau at large o is due to non convergence of the reciprocal space sum Redo the series of calculations using smaller kmax values The optimum values for kmax are the smallest values that reproduce the correct Coulombic energy the plateau value and virial at the value of o to be used in the simulation Note that one needs to specify the three integers kmaxi kmax2 kmax3 referring to the three spatial directions to ensure the reciprocal space sum is equally accurate in all directions The values of kmaxi kmax2 and kmax3 must be commensurate with the cell geometry to ensure the same minimum wavelength is used in all directions For a cubic cell set kmax1 kmax2 kmax3 However for example in a cell with dimensions 2A 2B C ie a tetragonal cell longer in the c direction than the a and b directions use 2kmaxl 2kmax2 kmax3 If the values for the kmax used are too small the Ewald sum will produce spurious results If values that are too large are used the results will be correct but the calculation will consume unnecessary amounts of cpu time The amount of cpu time increases with kmaxi x kmax2 x kmax3 CCLRC 96 3 4 DL POLY 2 Error Processing 3 4 1 The DL PO
57. 1071 metres i e Angstroms 3 The unit of mass mo is 1 6605402 x 10 kilograms i e atomic mass units 4 The unit of charge go is 1 60217733 x 10 coulombs i e unit of proton charge 5 The unit of energy E Mo lo to is 1 6605402 x 10 Joules 10 J mol 6 The unit of pressure Po Elz is 1 6605402 x 10 Pascal 166 05402 bar 7 Planck s constant A which is 6 350780668 x Eto In addition the following conversion factors are used The coulombic conversion factor Yo is EN dm q 18995 4835 Atego such that Uuks Eo YoU Internal Where U represents the configuration energy The Boltzmann factor kg is 0 831451115 E K such that T Eyin kp represents the conversion from kinetic energy in internal units to temperature in Kelvin Note In the DL POLY 2 OUTPUT file the print out of pressure is in units of kbars at all times The unit of energy is either DL POLY 2 units specified above or in other units specified by the user at run time The default is DL POLY units 1 3 12 Error Messages All errors detected by DL_POLY_2 during run time initiate a call to the subroutine ERROR which prints an error message in the standard output file and terminates the program All terminations of the program are global i e every node of the parallel computer will be informed of the termination condition and stop executing In addition to terminal error messages DL_POLY 2 will som
58. 17 1 9 Ede Units ee lt b oe Ge he ee E pe ah Eee SIEG Re xU Sedo s 18 1 3 12 Error Messages ce ecg eh BOE Ree xus ke e Re RO a Rog ug 18 14 The DL_POLY_2 Directory Structure eee 19 1 4 10 The source Sub directory 000 00 eee 19 1 4 The utility Sub directory eee 19 1 4 8 The data Sub directory 000000002 eG 19 1 44 The bench Sub directory 2 ees 19 1 4 5 The execute Sub directory o 20 1 4 6 The build Sub directory o ees 20 1 4 7 The public Sub directory e 20 1 4 8 The respa Sub directory o 00000 ee eee eee 20 1 4 9 The sdk Sub directory eA 20 1 5 Obtaining the Source Code leen 21 LO DEPRO DEN ia ter x oe AD o qx e gen irr dE d 22 lv Other Information vty ocelot EUR LR 22 OCCLRC 2 DL POLY 2 Force Fields and Algorithms 2 1 The DL_POLY_2 Force Field clle The Intramolecular Potential Functions 2 2 2 3 2 4 2 5 2 6 2 2 1 2 2 2 2 2 3 2 2 4 2 2 5 2 2 6 2 2 7 2 2 8 2 2 9 Bond Potentials o TE e e E aa ee Distance Restraints 2 2 0 0 0 0 00020000 Valence Angle Potentials Angular Restraints ee ee Dihedral Angle Potentials llle Improper Dihedral Angle Potentials Inversion Angle Potentials o Tethering Forces o Roe pe aree Up d ads AA edet
59. 2 Further Comments Note that recompiling DL POLY 2 with a different DL_PARAMS INC file may render any existing REVOLD file unreadable by the code 4 1 5 The TABLE File The TABLE file provides an alternative way of reading in the short range potentials in tabular form This is particularly useful if an analytical form of the potential does not exist or is too complicated to specify in the FORGEN subroutine The table file is read by the subroutine FORTAB see chapter 7 The option of using tabulated potentials is specified in the FIELD file see above The specific potentials that are to be tabulated are indicated by the use of the tab keyword on the record defining the short range potential see table 4 12 The directive vdwtable may be used in place of vdw to indicate that one or more of the short ranged potentials is specified in the form of a table 4 1 5 1 Format The file is fixed formatted with integers as 110 reals as el5 8 Character variables are read as a8 The header record is formatted as 80 alphanumeric characters 4 1 5 2 Definitions of Variables record 1 header a80 file header record 2 delpot real mesh resolution in cutpot real cutoff used to define tables ngrid integer number of grid points in tables The subsequent records define each tabulated potential in turn in the order indicated by the specification in the FIELD file Each potential is defined by a header record and a set of data re
60. A form of inversion potential has been encountered which DL POLY 2 does not recognise CCLRC 210 Action Locate the offending potential in the FIELD file and remove Replace with one acceptable to DL POLY 2 if this is reasonable Alternatively you may consider defining the required potential in the code yourself Amendments to subroutines SYSDEF and INVFRC will be required Message 450 error undefined tethering potential A form of tethering potential has been requested which DL_POLY_2 does not recognise Action Locate the offending potential in the FIELD file and remove Replace with one acceptable to DL_POLY_2 if this is reasonable Alternatively you may consider defining the required potential in the code yourself Amendments to subroutines SYSDEF and TETHFRC will be required Message 451 error three body potential cutoff undefined The cutoff radius for a three body potential has not been defined in the FIELD file Action Locate the offending three body force potential in the FIELD file and add the required cutoff Resubmit the job Message 452 error undefined pair potential A form of pair potential has been requested which DL POLY 2 does not recognise Action Locate the offending potential in the FIELD file and remove Replace with one acceptable to DL_POLY_2 if this is reasonable Alternatively you may consider defining the required potential in the code yourself Amendments to subroutines SYSDEF and FORGEN
61. A pointer array keytype Ntype type carries the indices of the specific atoms involved in the potential term labelled itype The dimension njype will be 2 3 or 4 if the term represents a bond angle or dihedral 4 The array Keytype Ntypes itype is used to identify the atoms in a bonded term and the appropriate form of interaction and thus to calculate the energy and forces Each processor is assigned the independent task of evaluating a block of Int Ntotat Nnodes interactions The same scheme works for all types of bonded interactions The global summation of the force arrays does not occur until all the force contributions including nonbonded forces has been completed 2 6 3 Distributing the Nonbonded Terms In DL_POLY_2 the nonbonded interactions are handled with a Verlet neighbour list 10 which is reconstructed at intervals during the simulation This list records the indices of all secondary atoms within a certain radius of each primary atom the radius being the cut off radius Teut normally applied to the nonbonded potential function plus an additional increment Arey The larger radius rcu Arc permits the same list to be used for several timesteps without requiring an update The frequency at which the list must be updated clearly depends on the thickness of the region Arc In RD the neighbour list is constructed simultaneously on each node and in such a way as to share the total burden of the work equally b
62. ACE CC xcc TIMER CPFLAGS D STRESS DMPI D POINTER integer OBJ_SPME EX EX BINROOT BINROOT TYPE Intel no SPME intel dpp MAKE FC if77 LD if77 o LDFLAGS node glob Knoieee FFLAGS c 02 CPFLAGS D STRESS DINTEL D POINTER integer OBJ_SPME EX EX BINROOT BINROOT TYPE Silicon Graphics 10000 Worskstation sgl0k dpp MAKE LD 90 o LDFLAGS 1scs FC f90 FFLAGS c 02 OPT Olimit 0 lscs TIMER CPFLAGS DCRAY D STRESS DSERIAL D POINTER integer EX EX BINROOT BINROOT TYPE Silicon Graphics 10000 Worskstation SPME via FFTW sglOk fftw dpp MAKE LD f90 o LDFLAGS 1scs lfftw lrfftw L FFTW LIBRARY FC f90 FFLAGS c 02 OPT Olimit 0 1scs TIMER CCLRC 166 CPFLAGS DCRAY D STRESS DSERIAL D POINTER integer DFFTW EX EX BINROOT BINROOT TYPE Silicon Graphics 8000 parallel sg8k mpi dpp cp usr include mpif h mpif h MAKE LD f90 03 64 o FC f90 LDFLAGS 1mpi TIMER FFLAGS c 03 64 CPFLAGS D STRESS DMPI DCRAY D POINTER integer EX EX BINROOT BINROOT TYPE Silicon Graphics 8000 parallel sg8k mpi f dpp cp usr include mpif h mpif h MAKE LD f90 Ofast 64 o FC
63. BINROOT The BINROOT keyword specifies the directory in which the executable is to be stored The default setting is execute 6 PVM NODES The PVM_NODES keywords specifies how many processes are to be invoked when the code is run under PVM There is no default value If this is not set at compile time the code will compile but produce an error message on execution If you get this error error 1 delete the module INITCOMMS O and recompile with PVM_NODES set to a number consistent with a hypercube architecture one of 1 2 4 8 etc CCLRC 87 3 2 1 2 Modifying the Makefile 1 Changing the TARGET If you do not intend to run DL_POLY_2 on one of the specified machines you must add appropriate lines to the makefile to suit your circumstances The safest way to do this is to modify an existing TARGET option for your purposes The makefile supplied with DL_POLY_2 contains examples for serial PVM and MPI environments as well as for Intel and Cray T3E parallel machines so you should find one close to your requirements You must of course be familiar with the appropriate invocation of the FORTRAN compiler for your local machine and also any alternatives to PVM or MPI your local machine may be running After DL POLY 2 Version 2 12 the required C preprocessor is supplied with the source code and is called dpp c written by J Genornowicz Southampton University 1999 If you wish to compile for MPI or PVM systems remember to ensure
64. D SHAKE 14 14 Hoover constant T P algorithm with RD SHAKE 16 15 Hoover constant T c algorithm with RD SHAKE 16 16 Berendsen constant T P algorithm with FIQA and RD SHAKE 14 17 Berendsen constant T P algorithm with QSHAKE 14 18 Berendsen constant T g algorithm with FIQA and RD SHAKE 14 19 Berendsen constant T c algorithm with QSHAKE 14 20 Hoover constant T P algorithm with FIQA and RD SHAKE 16 21 Hoover constant T P algorithm with QSHAKE 16 CCLRC 15 22 Hoover constant T g algorithm with FIQA and RD SHAKE 16 23 Hoover constant T g algorithm with QSHAKE 16 A variant of DL POLY 2 that handles the time reversible multiple timestep RESPA algorithm 17 18 is also available for atomic systems and rigid ion systems 19 but it is not applicable to systems which have rigid body molecules or constraints 1 3 Programming Style The programming style of DL_POLY_2 is intended to be as uniform as possible The following stylistic rules apply throughout Potential contributors of code are requested to note the stylistic convention 1 3 1 Programming Language Versions of DL POLY 2 prior to 2 11 are written exclusively in FORTRAN 77 Versions of DL_POLY_2 from 2 11 contain extensions written in FORTRAN 90 1 3 2 Memory Management Since version 2 11 of DL POLY 2 the major array dimensions are calculated at the time of execution and the associated arrays created through the dynamic array allocation fe
65. E algorithm is implemented in NVEQ_1 which allows for a system containing a mixture of rigid bodies and atomistic species provided the rigid bodies are not linked to other species by constraint bonds Thermostats and Barostats It is straightforward to couple the rigid body equations of motion to a thermostat and or barostat The thermostat is coupled to both the translational and rotational degrees of freedom and so both the translational and rotational velocities are propagated in an analogous manner to the thermostated atomic velocities The barostat however is coupled only to the translational degrees of freedom not to the rotational ones DL_POLY_2 supports both Hoover type and Berendsen thermostats and barostats for systems containing rigid bodies The Hoover thermostat is implemented in NVTQ H1 the Hoover isotropic barostat plus themostat in NPTQ_H1 and the anisotropic barostat in NPTQ H3 The analogous routines for the Berendsen algorithms are NVTQ Bl NPTQ B1 and NPTQ B3 2 5 6 3 Linked Rigid Bodies The above integration algorithm can be used for rigid bodies in a system containing atomic species whose equations of motion are integrated with the standard leapfrog algorithm These rigid bodies may even be linked to other species including other rigid bodies by extensible bonds However if a rigid body is linked to an atom or another rigid body by a bond constraint the above algorithm is not adequate The reason is that the
66. EX BINROOT BINROOT TYPE linux dpp MAKE FC f77 FFLAGS c N CPFLAGS D STRESS DSERIAL D POINTER integer qshake o MAKE LD f77 o LDFLAGS FC f77 FFLAGS c g CPFLAGS D STRESS DSERIAL D POINTER integer O0BJ SPME EX EX BINROOT BINROOT TYPE DEC Alpha no SPME dec alpha dpp MAKE LD f90 o FC f90 FFLAGS c fast LDFLAGS math library fast assume noaccuracy sensitive V CPFLAGS D STRESS DSERIAL D POINTER integer 8 TIMER OBJ_SPME EX EX BINROOT BINROOT TYPE DEC Alpha ev6 no SPME dec alpha ev6 dpp MAKE LD 90 o FC f90 FFLAGS c arch ev6 fast LDFLAGS arch ev6 math library fast assume noaccuracy sensitive CPFLAGS D STRESS DSERIAL D POINTER integer 8 TIMER OBJ_SPME EX EX BINROOT BINROOT TYPE Alpha Linux no SPME alpha linux dpp MAKE FC fort FFLAGS c 0 fast CPFLAGS D STRESS DSERIAL D POINTER integer 8 qshake o MAKE FC fort LD fort o FFLAGS c 0 fast CPFLAGS D STRESS DSERIAL D POINTER integer 8 LDFLAGS OBJ_SPME EX EX BINROOT BINROOT TYPE Alpha Linux plus SPME via FFTW alpha linux fftw dpp MAKE FC fort FFLAGS c 0 fast CPFLAG
67. Ewald sum precision When specifying the desired precision for the Ewald sum in the CONTROL file it is first necessary to specify the real space cutoff rcut Action Place the cut directive before the ewald precision directive in the CONTROL file and rerun Message 434 error illegal entry into STRESS related routine The calculation of the stress tensor in DL_POLY_2 requires additional code that must be included at compile time through the use of the STRESS keyword If this is not done and CCLRC 208 DL_POLY 2 is later required to calculate the stress tensor this error will result Action The program must be recompiled with the STRESS keyword activated This will ensure all the relevant code is in place See section 3 2 1 Message 436 error unrecognised ensemble An unknown ensemble option has been specified in the CONTROL file Action Locate ensemble directive in the CONTROL file and amend appropriately Message 438 error PMF constraints failed to converge The constraints in the potential of mean force algorithm have not converged in the permit ted number of cycles The SHAKE algorithm for PMF constraints is iterative Possible causes include a bad starting configuration too large a time step used incorrect force field specification too high a temperature inconsistent constraints involving shared atoms etc Action Corrective action depends on the cause It is unlikely that simply increasing the iteration
68. FCAP is sometimes required to reduce the magnitude of badly equilibrated forces Since DL POLY 2 is based on the replicated data strategy a global sum routine GDSUM is required to sum the atomic forces on all nodes Integration of the equations of motion is handled by one of the routines listed and described in section 2 5 For example routines NVE_0 NVT_EO NVT_HO NvT_BO etc are used if no constraint forces are present These routines treat the NVE Evans NVT Hoover Nos NV T and NV T Berendsen ensembles respectively The corresponding versions of these routines which handle constraint forces are NVE_1 NVT_El NVT_H1 or NVT_B1 These versions call the routine RDSHAKE_1 to handle the constraints RDSHAKE_1 itself calls a number of additional routines MERGE SHMOVE and SPLICE For ad hoc temperature scaling the routine VSCALEG is required As mentioned elsewhere DL POLY 2 does not contain many routines for computing system properties during a simulation Radial distributions may be calculated however using the routines RDF and RDF1 Similarly DIFFSNO and DIFFSN1 calculate approximate mean square displacements Ordinary thermodynamic quantities are calculated by the routine STATIC which also writes the S TATIS file section 4 2 7 Routine TRAJECT writes the HISTORY section 4 2 1 file for later analysis Job termination is handled by the routine RESULT which writes the final summaries in the OUTPUT file and dumps the restart files REVIVE
69. LY 2 Internal Error Facility DL POLY 2 contains a number of in built error checks scattered throughout the package which detect a wide range of possible errors In all cases when an error is detected the subroutine ERROR is called resulting in an appropriate message and termination of the program execution either immediately or after additional processing Users intending to insert new error checks should ensure that all error checks are per formed concurrently on all nodes and that in circumstances where a different result may obtain on different nodes a call to the global status routine GSTATE is made to set the appropriate global error flag on all nodes Only after this is done a call to subroutine ERROR may be made An example of such a procedure might be logical safe safe iest condition call gstate safe if not safe call error node id message number In this example it is assumed that the logical operation test condition will result in the answer true if it is safe for the program to proceed and false otherwise The call to ERROR requires the user to state the identity of the calling node node id so that only the nominated node in ERROR ie node 0 will print the error message The variable message number is an integer used to identify the appropriate message to be printed In all cases if ERROR is called with a non negative message number the program run terminates If the message number is negative execution c
70. R New Haven and London Yale University Press Sutton A P and Chen J 1990 Philos Mag Lett 61 139 Mayo S Olafson B and Goddard W 1990 J Phys Chem 94 8897 Smith W and Forester T R 1994 Comput Phys Commun 79 52 Smith W and Forester T R 1994 Comput Phys Commun 19 63 Allen M P and Tildesley D J 1989 Computer Simulation of Liquids Oxford Clarendon Press Ryckaert J P Ciccotti G and Berendsen H J C 1977 J Comput Phys 23 327 Fincham D 1992 Molecular Simulation 8 165 Forester T and Smith W 1995 In preparation Berendsen H J C Postma J P M van Gunsteren W DiNola A and Haak J R 1984 J Chem Phys 81 3684 Evans D J and Morriss G P 1984 Computer Physics Reports 1 297 Hoover W G 1985 Phys Rev A31 1695 Tuckerman M Berne B and Rossi A 1990 J Chem Phys 94 1465 156 CCLRC 157 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 Stuart S Zhou R and Berne B 1996 J Chem Phys 105 1426 Procacci P and Marchi M 1996 J Chem Phys 104 3003 Smith W 1998 Daresbury Laboratory Melchionna S and Cozzini S 1998 University of Rome Brode S and Ahlrichs R 1986 Comput Phys Commun 42 41 Hockney R W and Eastwood J W 1981 Computer Simulation Using Particles McGraw Hill Inte
71. R comparison The system consists of 3993 atoms in all and runs on 8 512 processors It uses neutral group electrostatics and rigid bond constraints and is one of the smallest benchmarks in the set 5 1 2 3 Benchmark 3 Simulation of the enzyme transferrin in 8102 water molecules The simulation makes use of neutral group electrostatics and rigid bond constraints The system is 27539 atoms and runs on 8 512 processors 5 1 2 4 Benchmark 4 Simulation of a sodium chloride melt with Ewald sum electrostatics and a multiple timestep algorithm to enhance performance The system is comprised of 27000 atoms and runs on 8 512 processors 5 1 2 5 Benchmark 5 Simulation of a sodium potassium disilicate glass Uses Ewald sum electrostatics a mul tiple timestep algorithm and a three body valence angle potentials to support the silicate structure It also using tabluated two body potentials stored in the file TABLE The system is comprised of 8640 atoms and runs on 16 512 processors 5 1 2 6 Benchmark 6 Simulation of a potassium valinomycin complex in 1223 water molecules using an adapted AMBER forcefield and truncated octahedral periodic boundary conditions The system size is 3838 atoms and runs on 16 512 processors CCLRC 143 5 1 2 7 Benchmark 7 Simulation of gramicidin A molecule in 4012 water molecules using neutral group elec trostatics The system is comprised of 12390 atoms and runs on 8 512 processors This example was provided by
72. S D STRESS DSERIAL D POINTER integer 8 qshake o CCLRC 164 MAKE FC fort LD fort o FFLAGS c 0 fast CPFLAGS D STRESS DSERIAL D POINTER integer 8 DFFTW V LDFLAGS 1fftw lrfftw L FFTW LIBRARY EX EX BINROOT BINROOT TYPE hp dpp MAKE FC 77 FFLAGS c CPFLAGS D STRESS DSERIAL D POINTER integer qshake o MAKE LD 77 o LDFLAGS FC f77 FFLAGS c 0 CPFLAGS D STRESS DSERIAL D POINTER integer 0BJ SPME EX EX BINROOT BINROOT TYPE H Convex HP exemplar serial no SPME exemplar dpp MAKE LD f90 o LDFLAGS FC f90 FFLAGS c ppu 02 DA2 0 CPFLAGS D STRESS DSERIAL D POINTER integer V 0BJ SPME TIMER EX EX BINROOT BINROOT TYPE HP PA 9000 C240 serial no SPME hp c240 dpp MAKE LD f90 o LDFLAGS FC f90 FFLAGS c ppu 02 DA2 0 CPFLAGS D STRESS DSERIAL D POINTER integer 0BJ SPME TIMER EX EX BINROOT BINROOT TYPE aix dpp MAKE FC mpxlf FFLAGS c NS2048 qarch pwr2 qnosave CPFLAGS D STRESS DSERIAL D POINTER integer intlist o MAKE LD x1f o LDFLAGS FC x1f FFLAGS c 03 NS2048 qarch pwr2 qnosave CPFLAGS D STRESS DSERIAL D POINTER integer V 0BJ SPME EX EX BINROOT BINROOT TYPE rs6k dpp MAKE LD x1f o LDFLAGS FC x1f FFLAGS c 0
73. SS DSERIAL D POINTER integer CFLAGS c 03 n32 mips4 r5000 EX EX BINROOT BINROOT TYPE sun dpp MAKE LD 77 o LDFLAGS FC f77 FFLAGS c 02 TIMER OBJ_SPME VN CPFLAGS D STRESS DSERIAL D POINTER integer EX EX BINROOT BINROOT TYPE Sun Ultra 2 serial no SPME sun ultra dpp MAKE LD opt SUNWspro bin f90 o LDFLAGS FC opt SUNWspro bin f90 FFLAGS c fnonstd xarch v8plusa xchip ultra 02 libmil dalign TIMER QBJ SPME CPFLAGS D STRESS DSERIAL D POINTER integer V EX EX BINROOT BINROOT TYPE Daresbury Beowulf Absoft compiler no SPME beowulf absoft dpp cp usr local lam 6 2 h mpif h mpif h MAKE LD usr bin f90 o N LDFLAGS L home kcm mpich absoft mpich lib LINUX ch_p4 lmpich FC usr bin f90 FFLAGS c 0 B100 TIMER OBJ_SPME CPFLAGS D STRESS DMPI P D POINTER integer I home kcm mpich absoft mpich include EX EX BINROOT BINROOT TYPE Interpolation tables options Default code Force tables interpolation in r space 3pt interpolation 3pt check OBJ_ALL OBJ_RRR 0BJ NEU 0BJ RIG 0BJ EXT TIMER 0BJ_SPME LD EXE 0BJ ALL 0BJ RRR 0BJ NEU 0BJ RIG 0BJ EXT TIMER LDFLAGS LDLIBS 0BJ_SPME CCLRC 168 Force tables interpolation in r space 4pt interpolation
74. THE DL POLY 2 USER MANUAL W Smith and T R Forester CCLRC Daresbury Laboratory Daresbury Warrington WA4 4AD England Version 2 12 Dec 1999 CCLRC 1 ABOUT DL_POLY DL_POLY is a parallel molecular dynamics simulation package developed at Daresbury Laboratory by W Smith and T R Forester under the auspices of the former Engineering and Physical Sciences Research Council EPSRC for the EPSRC s Collaborative Com putational Project for the Computer Simulation of Condensed Phases CCP5 and the Advanced Research Computing Group ARCG at Daresbury Laboratory The package is the property of The Council for the Central Laboratory of the Research Councils CCLRC DL_POLY is issued free under licence to academic institutions pursuing scientific research of a non commercial nature Commercial organisations may be permitted a licence to use the package after negotiation with the owners Daresbury Laboratory is the sole centre for distribution of the package Under no account is it to be redistributed to third parties without consent of the owners The purpose of the DL_POLY package is to provide software for academic research that is inexpensive accessible and free of commercial considerations Users have direct access to source code for modification and inspection In the spirit of the enterprise contributions in the form of working code are welcome provided the code is compatible with DL_POLY in regard to its interfaces and programming s
75. TIS file is appended at intervals determined by the stats directive in the CON TROL file The energy unit is as specified in the CONTROL file with the the units directive and are compatible with the data appearing in the OUTPUT file The contents of the appended information is record i nstep integer current MD time step time real elapsed simulation time nstepx At nument integer number of array elements to follow record ii stpval 1 stpval 5 engcns real total extended system energy i e the conserved quantity temp real system temperature engcfg real configurational energy engsrp real short range potential energy engcpe real electrostatic energy record iii stpval 6 stpval 10 engbnd real chemical bond energy engang real valence angle and 3 body potential energy engdih real dihedral interaction energy engtet real tethering energy enthal real enthalpy total energy PV record iv stpval 11 stpval 15 tmprot real rotational temperature vir real total virial virsrp real short range virial vircpe real electrostatic virial virbnd real bond virial record v stpval 16 stpval 20 virang real valence angle and 3 body virial vircon real constraint virial virtet real tethering virial volume real volume tmpshl real core shell temperature CCLRC record vi stpval 21 stpval 25 134 core shell potential energy core shell virial MD cell angle a MD cell angle 6 MD cell angle y Potential of Mean Force virial pressu
76. TORY File The HISTORY file is the dump file of atomic coordinates velocities and forces Its principal use is for off line analysis The file is written by the subroutines TRAJECT or TRAJECT_U The control variables for this file are ltraj nstraj istraj and keytrj which are cre ated internally based on information read from the traj directive in the CONTROL file see above The HISTORY file will be created only if the directive traj appears in the CONTROL file Note that the HISTORY file can be written in either a formatted or unformatted version We describe each of these separately below The HISTORY file can become very large especially if it is formatted For serious simulation work it is recommended that the file be written to a scratch disk capable of accommodating a large data file Alternatively the file may be written as unformatted below which has the additional advantage of speed However writing an unformatted file has the disadvantage that the file may not be readily readable except by the machine on which it was created This is particularly important if graphical processing of the data is required 4 2 1 1 The Formatted HISTORY File The formatted HISTORY file is written by the subroutine TRAJECT and has the following structure record 1 a80 header a80 file header record 2 2110 keytrj integer trajectory key see table 4 3 imcon integer periodic boundary key see table 4 6 natms integer number of atoms in simulat
77. The most recent wording appears below DL POLY 2 Versions 2 10 and Earlier Many of the DL_POLY_2 error messages refer to array bound checks and the user is advised to consider what other arrays may need to be altered when making the appropriate change If you are not familiar with DL POLY 2 the error messages will advise you as each array bound is violated but you will not be told of all errors in one pass Users are warned that reckless increases in the array dimensions are likely to result in the code being too large for any given memory A way to avoid many of these difficulties is to make use of the utility program PARSET see 6 1 1 which can greatly reduce the work required The standard user response when an array dimension error occurs is to locate the relevant parameter in the DL POLY 2 DL PARAMS INC file and increase the default number 176 CCLRC 177 It should be remembered that any change in a parameter specified in DL_PARAMS INC requires the whole program to be recompiled However the standard makefile provided in the build directory does this automatically DL_POLY_2 Versions 2 11 and Later Version 2 11 of DL_POLY_2 differs from previous versions in that it incorporates the func tionality of the utility code PARSET within the code itself and uses FORTRAN 90 dynamic array allocation to set the array sizes at run time This is a considerable advance on previ ous practice and means that a single executable may be com
78. U 11 22 s EN y Ubona ibond La o lbona 1 Nangle F y Uangle iangle La Tb Le langle l Ndihed Y Udinedlidineds Tas Ts Tos La tdihed 1 Ninv EE Uinu inv Ta To Tc La linvu 1 N 1 N y 5 Usair 1 j Ir tl i 1 gt N 2N 1 N Y Y Us oa is j k ro Tj TX i l j i k j N 3N 2N 1 N m y 5 y 5 Ua_bodyli j k n Tj Lj p Ln i 1 j i k j n k N tM Us iri Ys 2 1 i 1l where Ubond Uangie Udineas Uinv Upair U3_body and Ua body are empirical interaction functions representing chemical bonds valence angles dihedral angles inversion angles pair body three body and four body forces respectively The first four are regarded by DL_POLY_2 as intra molecular interactions and the next three as inter molecular interac tions The final term Uezin represents an external field potential The position vectors Tay Tp c and rg refer to the positions of the atoms specifically involved in a given interac tion Almost universally it is the differences in position that determine the interaction The numbers Noond Nangle Nainea and Niny refer to the total numbers of these respective interactions present in the simulated system and the indices tbond tangle tiny and dihed uniquely specify an individual interaction of each type It is important to note that there is CCLRC 26 no global specification of the intramolecular interactions in DL_POLY_2 all bonds valence angles and dihedrals must be individua
79. a catalogue of instantaneous values of thermodynamic and other variables in a form suitable for temporal or statistical analysis Finally the HISTORY file section 4 2 1 provides a time ordered sequence of configurations to facilitate further anal ysis of the atomic motions Depending on which version of the TRAJECT subroutine you compiled in the code this file may be either formatted human readable or unformatted You may move these output files back into the data sub directory using the store macro found in the execute sub directory Note that versions of DL POLY 2 after 2 10 may also create the files RDFDAT and ZDNDAT containing the RDF and Z density data respectively They are both human readable files CCLRC 91 3 2 4 Restarting DL_POLY_2 The best approach to running DL_POLY_2 is to define from the outset precisely the simula tion you wish to perform and create the input files specific to this requirement The program will then perform the requested simulation but may terminate prematurely through error inadequate time allocation or computer failure Errors in input data are your responsibil ity but DL_POLY_2 will usually give diagnostic messages to help you sort out the trouble Running out of job time is common and provided you have correctly specified the job time variables using the close time and job time directives see section 4 1 1 in the CON TROL file DL POLY 2 will stop in a controlled manner allowing you to restar
80. al is obtained using the general formula o S ET Tij 2 9 Lj Tij The force f acting on atom is the negative of this The contribution to be added to the atomic virial is given by W r fy 2 10 with only one such contribution from each bond The contribution to be added to the atomic stress tensor is given by Pdo 2 11 where o and f indicate the x y z components The atomic stress tensor derived in this way is symmetric In DL_POLY_2 bond forces are handled by the routine BNDFRC Note some DL POLY_2 routines may use the convention that rij r Tj CCLRC 29 2 2 2 Distance Restraints In DL_POLY_2 distance restraints in which the separation between two atoms is main tained around some preset value rg is handled as a special case of bond potentials As a consequence distance restraints may be applied only between atoms in the same molecule Unlike with application of the pure bond potentials the electrostatic and van der Waals interactions between the pair of atoms are still evaluated when distance restraints are ap plied All the potential forms of the previous section are avaliable as distance restraints although they have different key words 1 Harmonic potential hrm 2 Morse potential mrs 12 6 potential bond 126 Restrained harmonic rhm cU Ae WwW Quartic potential qur In DL_POLY_2 distance restraints are handled by the routine BNDFRC 2 2 3 Valence Angle Pote
81. ale ok ale ade al ale ok ale ode k a ok 2k ok ok ok ok ale ale ale ok ok ok ale oe ok a ale ade ale ok ok a ok ale ale ok ok ade ale ale ale ok ok ok ale ok a ok ale ade ale ae ad oe ok ale k ak k c c dl_poly insert file specifying array sizes for the c entire package c c copyright daresbury laboratory 1994 c authors w smith amp t forester november 1994 c c c note the following internal units apply everywhere c c unit of time to 1 x 10 12 seconds c unit of length lo 1 x 10 10 metres c unit of mass mo 1 6605402 x 10 27 kilograms c unit of charge qo 1 60217733 x 10 19 coulombs c unit of energy Eo 1 6605402 x 10 23 joules c unit of pressure Po 1 6605402 x 10 7 pascals c 163 842151 atmospheres c Cad k kk k ade ad ale ale ok ade ade ale ale ok ale ole ak k ok ale ale ok ok ok ale ale ale ok ok ade ale oe ok a ale ade ale ok ok a ok ale ok ok ok ok ale ale ale ok ok ok ale ok ok ok ale ade ale ok ok oe ok ale k ak 2k C 7 1 1 2 Function The DL_POLY_2 parameters file for version 2 10 and earlier contains all the parameters defining the arrays dimensions of DL_POLY_2 plus the fundamental constants and conver sion factors In the include file for version 2 11 and after the bulk of these parameters take the form of FORTRAN integer variables which are stored in the COMMON block params Apart from this difference the meaning and function of the parameters is the sa
82. all The number of sites defined in the potential of mean force is too large The dimensions of the appropriate arrays in DL_POLY_2 must be increased Action Standard user response Fix the parameter mxspmf Message 462 error PMF UNIT record expected A pmf unit directive was expected as the next record in the FIELD file but was not found Action Locate the pmf directive in the FIELD file and examine the following entries Insert the missing pmf unit directive and resubmit CCLRC 212 Message 464 error thermostat time constant must be gt 0 d0 A zero or negative value for the thermostat time constant has been encountered in the CONTROL file Action Locate the ensemble directive in the CONTROL file and assign a positive value to the time constant Message 466 error barostat time constant must be gt 0 d0 A zero or negative value for the barostat time constant has been encountered in the CON TROL file Action Locate the ensemble directive in the CONTROL file and assign a positive value to the time constant Message 468 error r0 too large for snm potential with current cutoff The specified location r0 of the potential minimum for a shifted n m potential exceeds the specified potential cutoff A potential with the desired minimum cannot be created Action To obtain a potential with the desired minimum it is necessary to increase the van der Waals cutoff Locate the rvdw directive in the CONTROL file a
83. all contri butions to the energy including system extensions due to thermostats etc It is nominally the conserved variable of the system and is not to be confused with conventional system energy which is a sum of the kinetic and configuration energies The interval for printing out these data is determined by the directive print in the CONTROL file At each time step that printout is requested the instantaneous values of CCLRC 130 the above statistical variables are given in the appropriate columns Immediately below these three lines of output the rolling averages of the same variables are also given The maximum number of time steps used to calculate the rolling averages is determined by the parameter mxstak in the DL PARAMS INC file see section 7 1 1 The working number of time steps for rolling averages is controlled by the directive stack in file CONTROL see above The default value is mxstak Energy Units The energy unit for the data appearing in the OUTPUT is defined by the units directive appearing in the CONTROL file Pressure units The unit of pressure is k bar irrespective of what energy unit is chosen 4 2 2 6 Summary of Statistical Data This portion of the OUTPUT file is written from the subroutine RESULT The number of time steps used in the collection of statistics is given Then the averages over the production portion of the run are given for the variables described in the previous section The root mean square
84. an tabulation in r This is to ensure sufficient accuracy is retained at small r A guide to the minimum number of grid points mxgrid required for interpolation in r to give good energy conservation in a simulation is mxgrid gt 100 rcut rmin CCLRC 89 where rmin is the smallest position minimum of the non bonded potentials in the sys tem The parameter mxgrid is defined in the DL_PARAMS INC file and must be set before compilation 2 A guide to the minimum number of grid points required for interpolation in r is mxgrid gt 100 rcut rmin where rmin is again the smallest position minimum of the non bonded potentials in the system For users in doubt as whether to use r or r space interpolation we recommend the former This is because tabulation in r is less demanding on memory requirements and less prone to inaccuracy should too small a value of mxgrid or too large a value of rcut be used Tabulation in r is therefore the default option for DL POLY r interpolation can be specified at compile time by making the executable with the directive TYPE rsq The other issue of concern to users is the choice of 3 or 4 point schemes in r space in terpolation The relative merits are as follows 4 point interpolation may permit a smaller number of grid points to be used in the interpolation tables thus saving on memory require ments 3 point interpolation is quicker than 4 point interpolation and normally sufficiently accurat
85. and the discrete Fourier transform of Q ki ko k3 4 Calculating the atomic forces which are given formally by 0Q k ka k3 ore OU recip 1 2 144 ore Vo o TN Fortunately due to the recursive properties of the B splines these formulae are easily evaluated The virial and the stres tensor are calculated in the same manner as for the conventional Ewald sum 2 4 7 Reaction Field In the reaction field method it is assumed that any given molecule is surrounded by a spherical cavity of finite radius within which the electrostatic interactions are calculated explicitly Outside the cavity the system is treated as a dielectric continuum The occurence of any net dipole within the cavity induces a polarisation in the dielectric which in turn interacts with the given molecule The model allows the replacement of the infinite Coulomb sum by a finite sum plus the reaction field CCLRC 54 The reaction field model coded into DL_POLY_2 is the implementation of Neumann based on charge charge interactions 32 In this model the total Coulombic potential is given by 1 4T 9 U E Taj 2R2 X aan j n 2 145 where the second term on the right is the reaction field correction to the explicit sum with Re the radius of the cavity The constant Bo is defined as _ 611 Qe x1 2 146 with e the dielectric constant outside the cavity The effective pair potential is therefore Taj 2R2 T
86. ar dynamics We therefore thought it worthwhile to tap into this expertise to produce a new package The third reason was that we thought it would be valuable to produce a package that was entirely free from commercial constraints by which we mean the source code would be available to academic institutions for adaptation and extension There would be no restriction preventing users from examining and verifying the source code DL_POLY was not to be a black box Of course in a rapidly developing subject area we cannot guarantee we have everything a potential user may need However since this is very much a project endorsed by CCP5 which serves the UK and World Wide academic community we are also hopeful that our users will be inclined to contribute any extensions of the package they devise and so accel erate its development As it stands the package has some nice features we believe While it is designed for distributed memory parallel machines we have taken care to ensure that it can with minimum modification be run on the popular workstations Scaling up a sim ulation from a small workstation to a massively parallel machine remains straightforward This ought to encourage novices to take up parallel computing Users are reminded that we are interested in hearing what other features could be usefully incorporated We obviously have ideas of our own and CCP5 strongly influences developments but other input would be welcome nevertheless
87. ard Verlet neighbour list and a smaller cutoff rprim which is used to define a primary list within the larger cutoff sphere see figure Forces derived from atoms in the primary list are generally much larger than those derived from remaining so called secondary atoms in the neighbour list Good energy conservation is therefore possible if the forces derived from the primary atoms are calculated every timstep while those from the secondary atoms are calculated much less frequently and are merely extrapolated over the interval DL POLY 2 handles this procedure as follows DL POLY 2 updates the Verlet neighbour list at irregular intervals determined by the movement of atoms in the neighbour list see section 2 1 The interval between updates is usually of the order of 20 timesteps Partitioning the Verlet list into primary and secondary atoms always occurs when the Verlet list is updated and thereafter at intervals of multt timesteps ie the multi step interval specified by the user see section 4 1 1 Immediately after the partitioning the force contributions from both the primary and secondary atoms are calculated The forces are again calculated in total in the subsequent timestep Thereafter for multt 2 timesteps the forces derived from the primary atoms are calculated explicitly while those derived from the secondary atoms are calculated by linear extrapolation of the exact forces obtained in the first two timesteps of the multi step in
88. are three variables that control the accuracy o the Ewald convergence parameter Teut the real space forces cutoff and the kmax1 2 3 integers that effectively define the range of the reciprocal space sum one integer for each of the three axis directions These variables are not independent and it is usual to regard one of them as pre determined and adjust the other two accordingly In this treatment we assume that freut defined by the cutoff directive in the CONTROL file is fixed for the given system The Ewald sum splits the electrostatic sum for the infinite periodic system into a damped real space sum and a reciprocal space sum The rate of convergence of both sums is governed by a Evaluation of the real space sum is truncated at r Teut so it is important that a be chosen so that contributions to the real space sum are negligible for terms with r gt ra The relative error e in the real space sum truncated at reut is given approximately by amp erfc orcuc reus Y expl o reus reus 3 1 The recommended value for is 3 2 reu or greater too large a value will make the reciprocal space sum very slowly convergent This gives a relative error in the energy of no greater than e 4x 107 in the real space sum When using the directive ewald precision DL POLY 2 makes use of more sophisticated approximation erfc a 0 56 exp a x 3 2 Important note For the SPME method the values of kmax1 2 3 should be double t
89. at ate A4 The REVOLD File ics sega tov ak bow ech ee ae en Ee OPER 4 1 5 The TABLE File 4 2 The OUTPUT Files 4 2 1 The HISTORY File leen 4 22 The OUTPUT Piles 4er A we ee EIS 4 2 3 The REVCON File o e e 4 2 4 The REVIVE File 43 5 The RDEDAT lO 2e whet Cnt cb ao rd Bde 4 2 0 The Z DNDAT File tea ee ee Gan eg R ud 4 2 7 The STATIS File 5 DL_POLY_2 Examples 5 1 DL POLY Examples 5 1 1 Test Cases 5 1 2 Benchmark Cases OCCLRC 6 DL POLY 2 Utilities 6 1 Miscellaneous Utilities Al SPARSET A A caa ay ears wey S INA CEN 6 1 2 UsefulMacros A 7 DL POLY 2 Subroutines and Functions 7 1 Subroutine and Function Specifications 7 1 1 DL PARAMS INC The DL POLY Parameters Include File A The DL POLY 2 Makefile B Periodic Boundary Conditions in DL POLY C DL_POLY Error Messages and User Action 144 145 145 147 150 152 152 159 170 176 Chapter 1 Introduction CCLRC 10 Scope of Chapter This chapter describes the concept design and directory structure of DL_POLY_2 and how to obtain a copy of the source code CCLRC 11 1 1 The DL_POLY Package DL POLY 2 DL_POLY 1 is a package of subroutines programs and data files designed to facilitate molecular dynamics simulations of macromolecules polymers ionic systems and solutions on a distributed memory parallel computer The first version
90. ature of rigid species comprising the charged groups but is confined to free atoms or flexible molecules in the same system you may consider overriding this error message and continuing with your simulation The appropriate error trap is found in subroutine SYSDEF Message 99 error cannot use shell model with constraints The dynamical shell model was not designed to work in conjunction with constraint bonds This error results if both are used in the same simulation Action There is no general remedy if you wish to combine both these capabilities However if your simulation does not require the polarisability to be a feature of the constrained species but is confined to free atoms or flexible molecules you may consider overriding this error message and continuing with your simulation The appropriate error trap is in subroutine SYSDEF Message 100 error forces working arrays too small There are a number of arrays in DL POLY_2 that function as workspace for the forces cal culations Their dimension is equal to the number of atoms in the simulation cell divided by the number of nodes If these arrays are likely to be exceeded DL_POLY_2 will terminate execution Action Standard user response Fix the parameter msatms Message 101 error calculated 4 body potential index too large DL_POLY_2 has a permitted maximum for the calculated index for any four body potential in the system ie as defined in the FIELD file If there a
91. atures of FORTRAN 90 In versions prior to 2 11 array dimensions are fixed at compilation time and defined by FORTRAN PARAMETER statements 1 3 3 Target Computers DL POLY 2 is targeted towards distributed memory parallel computers However versions of the program for serial computers are easily produced To facilitate this all machine specific calls are located in dedicated FORTRAN routines to permit substitution by ap propriate alternatives or even deletion DL POLY 2 will run on the the following computers 1 Cray T3D 2 Cray T3E 3 DEC Alpha 4 HP 9000 Series 5 Hitachi SR2201 6 IBM RS6000 7 IBM SP 2 CCLRC 16 8 Intel iPSC 860 9 SUN SPARC and ULTRA SPARC 10 Silicon Graphics machines all kinds Porting of DL_POLY_2 to these and other machines requires PVM or MPI message passing tools with the exception of Intel distributed memory machines 1 3 4 Version Control System CVS DL_POLY_2 was developed with the aid of the CVS version control system We strongly recommend that users of DL_POLY_2 adopt this system for code development particularly where several users access the same source code For information on CVS please contact info cvs requestQprep ai mit edu 1 3 5 Required Program Libraries DL POLY 2 is for the most part self contained and does not require access to many additional program libraries The required program libraries for parallel execution are either PVM or MPI we recommend the
92. based on the assumption that the system is reasonably isotropic beyond the cutoff In DL_POLY_2 the short ranged forces are calculated by one of the routines SRFRCE SRFRCE_RSQ and SRFRCENEU The long range corrections are calculated by routine LR CORRECT The calculation makes use of the Verlet neighbour list described above CCLRC 42 2 3 2 Metal Potentials DL POLY 2 includes density dependent potentials suitable for calculating the properties of metals The basic model is due to Finnis and Sinclair 28 as implemented by Sutton and Chen 6 The form of the potential is stch 0 E SJ exa 2 86 izj NI where the local density p is given by pi Y 2 87 The Sutton Chen potential has the advantage that it is decomposable into pair contributions and thus falls within the general tabulation scheme of DL_POLY_2 where it is treated as a short ranged interaction The same form of potential may be used in alloys through the appropriate choice of parameters e and a The parameters n and m however must be the same for all component elements DL_POLY_2 calculates this potential in two stages the first calculates the local density p for each atom and the second calculates the potential energy and forces Interpolation arrays are used in both these stages The total force I on an atom j derived from this potential is calculated in the standard way ba M Use 2 88 ES ON OTN a AN dj El 5 20 ae amp IC A EM 14 j
93. constraint will introduce an additional force and torque onto the body that can only be found after the integration of the unconstrained unit DL POLY 2 has a suite of integra tion algorithms to cope with this situation in which both the constraint conditions and the quaternion equations are solved similtaneously using an extension of the SHAKE algorithm called QSHAKE 13 The QSHAKE algorithm proceeds as follows Consider the figure in which two rigid bodies are linked by a constraint bond We seek to choose Fons so that at the end of the integration step the two sites in the constraint bond are a distance r apart The integration of the bodies as free units leaves the sites r apart Since the constraint force produces both a force and torque on the rigid units the correction to the constrained sites position must include both the translation and rotation of the body as whole The translational contribution is 1 Azry ANTE zz 2 199 The torque induced by the constraint force is Tconst d x I edt 2 200 so the correction to the angular velocity of the body is Aw At I nag 2 201 CCLRC 69 The rotational correction to the position of the site is thus Az At Aw x da 2 202 which in general will not be in the same direction as Fong and Agy If we denote the components of Agp parallel and perpendicular to Fong by Az and Azl the correction to the site position is Az Agr Az Ark 2 203 Clearl
94. cords with the potential and force tables header record atom 1 a8 first atom type atom 2 as second atom type potential data records number of data records Int ngrid 3 4 data 1 real data item 1 data 2 real data item 2 data 3 real data item 3 data 4 real data item 4 force data records number of data records Int ngrid 3 4 data 1 real data item 1 CCLRC 124 data 2 real data item 2 data 3 real data item 3 data 4 real data item 4 4 1 5 3 Further Comments It should be noted that the number of grid points in the TABLE file should not be less than the number of grid points DL_ POLY _2 is expecting This number is given by the parameter mxgrid in the DL_PARAMS INC file see section 7 1 1 DL_POLY_2 will re interpolate the tables if ngrid gt mxgrid but will abort if ngrid lt mxgrid The potential and force tables are used to fill the internal arrays vvv and ggg respectively see section 2 3 1 The contents of force arrays are derived from the potential via the formula G r SU Note this is not the same as the true force CCLRC 125 4 2 The OUTPUT Files DL POLY 2 produces up to seven output files HISTORY OUTPUT REVCON REVIVE RDFDAT ZDNDAT and STATIS These respectively contain a dump file of atomic co ordinates velocities and forces a summary of the simulation the restart configuration statistics accumulators radial distribution data Z density data and a statistical history 4 2 1 The HIS
95. ction Check the specified simulation cell vectors and correct accordingly Message 135 error incorrect hexagonal prism boundary condition When calculating minimum images DL_POLY_2 checks that the periodic boundary of the simulation cell is compatible with the specifed minimum image algorithm Program termi nation results if an inconsistency is found In this case the error refers to the hexagonal prism minimum image which is inconsistent with the simulation cell The most probable cause is the incorrect definition of the simulation cell vectors present in the input file CON FIG these must equal the vectors of the enscribing orthorhombic cell Action Check the specified simulation cell vectors and correct accordingly Message 140 error incorrect dodecahedral boundary condition When calculating minimum images DL_POLY_2 checks that the periodic boundary of the simulation cell is compatible with the specifed minimum image algorithm Program ter mination results if an inconsistency is found In this case the error refers to the rhombic dodecahedral minimum image which is inconsistent with the simulation cell The most probable cause is the incorrect definition of the simulation cell vectors present in the input file CONFIG these must equal the vectors of the enscribing tetragonal simulation cell Action Check the specified simulation cell vectors and correct accordingly Message 145 error no van der waals potentials defined T
96. ctrostatics restart job from end point of previous run i e continue current simulation restart job from previous run with temperature scaling i e begin a new simulation from older run rescale atomic velocities every n steps during equilibration set shake tolerance to f default 1078 calculate electrostatic forces using shifted coulombic potential select Ewald sum for electrostatics with automatic parameter optimisation 0 f 5 spme sum a k1 k2 k3 stack n stats n steps n temp f traj ijk timestep f zden Zero select Ewald sum for electrostatics with a Ewald convergence parameter 71 k1 maximum k vector index in x direction k2 maximum k vector index in y direction k3 maximum k vector index in z direction set rolling average stack to n timesteps accumulate statistics data every n timesteps run simulation for n timesteps set required simulation temperature to f K write HISTORY file with controls i start timestep for dumping configurations j timestep interval between configurations k data level i e variable keytrj see table 4 3 set timestep to f ps calculate the z density profile perform zero temperature MD run 4 1 1 3 Further Comments on the CONTROL File 1 A number of the directives or their mutually exclusive alternatives are manda tory a timestep specifying the simulation timestep b temp or zero specifying the system temperature not mutually exclusive
97. d 7 hbnd U bjir Dnscos 05 b ps r5k 6 Ras rin Y 2 102 Note that for the hydrogen bond the hydrogen atom must be the central atom Several of these functions are identical to those appearing in the intra molecular valenceangle de scriptions above There are significant differences in implementation however arising from the fact that the three body potentials are regarded as inter molecular Firstly the atoms involved are defined by atom types not specific indices Secondly there are no excluded atoms arising from the three body terms The inclusion of pair potentials may in fact be essential to maintain the structure of the system The three body potentials are very short ranged typically of order 3 This property plus the fact that three body potentials scale as N where N is the number of particles makes it essential that these terms are calculated by the link cell method 29 The calculation of the forces virial and stress tensor as described in the section valence angle potentials above DL POLY 2 applies no long range corrections to the three body potentials The three body forces are calculated by the routine THBFRC 2 3 4 Four Body Potentials The four body potentials in DL POLY 2 are entirely inversion angle forms primarily in cluded to permit simulation of amorphous materials particularly borate glasses The potential forms available in DL POLY 2 are as follows 1 Harmonic harm U dijkn
98. d at compile time using an appropriate makefile The subroutines in this sub directory are documented in chapter 7 1 4 2 The utility Sub directory This sub directory stores all the utility subroutines functions and programs in DL POLY 2 together with examples of data The various routines in this sub directory are documented in chapter 6 of this manual Users who devise their own utilities are advised to store them in the utility sub directory 1 4 3 The data Sub directory This sub directory contains examples of input and output files for testing the released version of DL POLY 2 The examples of input data are copied into the ezecute sub directory when a program is being tested The test cases are documented in chapter 5 1 4 4 The bench Sub directory This directory contains examples of input and output data for DL POLY 2 that are suitable for benchmarking DL_POLY_2 on large scale computers These are described in chapter 5 CCLRC 20 1 4 5 The execute Sub directory In the supplied version of DL_POLY_2 this sub directory contains only a few macros for copying and storing data from and to the data sub directory and for submitting programs for execution These are decribed in section 6 1 2 However when a DL_POLY_2 program is assembled using its makefile it will be placed in this sub directory and will subsequently be executed from here The output from the job will also appear here so users will find it convenient to use t
99. d by three variables the real space cutoff reut the convergence parameter o and the largest reciprocal space vector kmar Used in the reciprocal space sum These are discussed more fully in section 3 3 5 DL POLY 2 can provide estimates if requested see CONTROL file description 4 1 1 The force on an atom 7 is obtained by differentiation and is dj exp k 4a fj E Y ikexp k c SCA Sog ik r4 k40 dn 20 nj 2 2 j er f c or exp 0 Tai Tq 2 133 felon m exp arh rajo 2 35 Nor 207 p em 2 ferflary P3 exp o rdj bry The electrostatic contribution to the system virial can be obtained as the negative of the Coulombic energy However in DL POLY 2 this formal equality can be used as a check on the convergence of the Ewald sum The actual electrostatic virial is obtained during the calculation of the diagonal of the stress tensor The electrostatic contribution to the stress tensor is given by OO j 1 1 exp E g aA zs Pru E PGA lE geni rjr 2 gt Y ue ferfe arn e experi Raj 2 134 jen Taj M qu 2orpj Arey ferf are 273 exp o r7 j Rg j t ti CCLRC 52 where matrices K and Ry are defined as follows Ke kek 2 135 n rere 2 136 In DL_POLY_2 the full Ewald sum is handled by several routines EWALD1 and EWALD1A handle the reciprocal space terms EWALD2 EWALD2_2PT EWALD2_RSQ and EWALD4 EWALD4_2PT handle the real spac
100. d estimate the required array sizes A description of the individual arrays found in DL POLY 2 is provided in Appendix C of the DL POLY 2 Reference Manual CCLRC 81 In versions preceeding 2 11 the size of the DL_POLY_2 executable is determined by the the DL_PARAMS INC include file see section 7 1 1 which specifies all the FORTRAN parameters of the code and is included in each subroutine at compile time This file is found in the source directory and is internally documented it is also documented in chapter 7 Reconstructing the DL PARAMS INC for a new simulation is the most difficult aspect of preparing a DL_POLY_2 executable If the parameters are not appropriate DL_POLY_2 will complain if any parameter is too small and abort in execution Each such error will entail a recompilation of the code and DL_POLY_2 generally detects only one error at a time Fortunately the process of creating a new DL_PARAMS INC file is greatly assisted by the utility program PARSET see section 6 1 1 Provided the CONTROL CONFIG and FIELD files are available PARSET will create a suitable parameters file for you See section 3 2 2 3 1 2 Constructing Nonstandard Versions In constructing a nonstandard DL_POLY_2 simulation program the first requirement is for the user to write a program to function as the root segment The source directory contains an example of such a root program DLPOLY This root program calls the major routines required to perfor
101. d key ad see table 4 7 index 1 integer first atomic site in bond index 2 integer second atomic site in bond variable 1 real potential parameter see table 4 7 variable 2 real potential parameter see table 4 7 variable 3 real potential parameter see table 4 7 variable 4 real potential parameter see table 4 7 The meaning of these variables is given in table 4 7 This directive and associated data records need not be specified if the molecule contains no flexible chemical bonds See the note on the atomic indices appearing under the shell directive above Table 4 7 Chemical bond potentials key potential type Variables 1 4 functional form Harmonic 1 2 U r Eo 1 exp k r ro 1 U r 54 amp Restraint TQ U r k r ro lr ro re U r 5kr2 kr Jr ro re r ro gt re ee ro E RY U r 8r ro 5r ro er ro Note bond potentials with a dash as the first character of the keyword do not con tribute to the excluded atoms list see section 2 1 In this case DL POLY 2 will also calculate the nonbonded pair potentials between the described atoms unless these are deactivated by another potential specification 6 constraints n where n is the number of constraint bonds in the molecule Each of the following n records contains index 1 integer first atomic index index 2 integer second atomic index bondlength real constraint bond length CCLRC 115 This
102. derscore If this is the case the flag DMPIU must be included as part of the C preprocessing flags and the file mpif h copied from the MPI library directory into the source directory Alternatively you can set the path to the MPI library either the I option on the C preprocessing flags The DL_POLY_2 makefile assumes you have copied the file over see the entry hp mpi in the makefile This appends an underscore to all MPI subroutine names and to the name of the MPI common block If the underscores are not required the flag must be omitted see the entry sp2 mpi CCLRC 88 When using MPI you need a copy of the MPI include file mpif h in the source directory On many machines this is stored in the usr include directory in which case the make procedure should find it automatically as it also does for IBM SP 2 and Cray T3E machines where it is stored elsewhere However if the make reports a failure to find the mpif h file you must amend the makefile to ensure that it copied from the true location before C preprocessing is attempted There are several examples in the makefile of how this is done Similarly when using PVM you need to place a copy of the PVM include file pvmf h in the source directory or copy it in before C preprocessing 4 Problems with optimization Some subroutines do not compile correctly when using optimization on some com pilers This is not the fault of the DL_POLY_2 code but of th
103. dinate origin is the centre of the MD cell The parallelepiped boundary condition can be used with the Ewald summation method Truncated octahedral boundaries IMCON 4 CCLRC 173 The truncated octahedral MD cell This is one of the more unusual MD cells available in DL_POLY but it has the advantage of being more nearly spherical than most other MD cells This means it can accommodate a larger spherical cutoff for a given number of atoms which leads to greater efficiency This can be very useful when simulating for example a large molecule in solution where fewer solvent molecules are required for a given simulation cell width The principal axes of the truncated octahedron see figure pass through the centres of the square faces and the width of the cell measured from square face to square face along a principal axis defines the width D of the cell From this the cell vectors required in the DL_POLY_2 CONFIG file are simply D 0 0 0 D 0 0 0 D These are also the cell vectors defining the enscribing cube which posseses twice the volume of the truncated octahedral cell Once again the atomic positions are defined with respect to the cell centre The truncated octahedron can be used with the Ewald summation method Rhombic dodecahedral boundaries IMCON 5 This is another unusual MD cell see figure but which possesses similar advantages to the truncated octahedron but with a slightly greater efficiency in its use of t
104. directive and associated data records need not be specified if the molecule contains no constraint bonds See the note on the atomic indices appearing under the shell directive above 7 pmf b where b is the potential of mean force bondlength A There follows the definitions of two PMF units a pmf unit n where n is the number of sites in the first unit The subsequent n records provide the site indices and weighting Each record contains index integer atomic site index weight real site weighting b pmf unit n2 where na is the number of sites in the second unit The subsequent na records provide the site indices and weighting Each record contains index integer atomic site index weight real site weighting This directive and associated data records need not be specified if no PMF con straints are present See the note on the atomic indices appearing under the shell directive above The pmf bondlength applies to the distance between the centres of the two pmf units The centre R of each unit is given by where r is a site position and we the site weighting Note that the pmf constraint is intramolecular To define a constraint between two molecules the molecules must be described as part of the same DL POLY molecule This is illustrated in test case 6 where a pmf constraint is imposed between a potassium ion and the centre of mass of a water molecule DL POLY 2 allows only one type of pmf constraint per system
105. e CCLRC 184 Action Standard user response Fix the parameter mxcons Message 42 error transfer buffer too small in mergel The buffer used to transfer data between nodes in the MERGE1 subroutines has been di mensioned too small Action Standard user response Fix the parameter mxbuff Message 45 error too many atoms in CONFIG file DL POLY 2 limits the number of atoms in the system to be simulated and checks for the violation of this condition when it reads the CONFIG file Termination will result if the condition is violated Action Standard user response Fix the parameter mxatms Consider the possibility that the wrong CONFIG file is being used e g similar system but larger size Message 46 ewlbuf array too small in ewald1 The ewlbuf array used to store structure factor data in subroutine EWALD1 has been di mensioned too small Action Standard user response Fix the parameter mxebuf Message 47 error transfer buffer too small in merge The buffer used to transfer data between nodes in the MERGE subroutines has been dimen sioned too small Action Standard user response Fix the parameter mxbuff Message 48 error transfer buffer too small in fortab The buffer used to transfer data between nodes in the FORTAB subroutines has been dimen sioned too small Action Standard user response Fix the parameter mxbuff CCLRC 185 Message 49 error frozen core shell unit specified Th
106. e Benzene etc Rigid molecular ions with point charges e g KNO3 NH 1 2504 etc Polymers with rigid bonds e g C Han 2 X Oc C Polymers with rigid bonds and point charges e g proteins 00 Macromolecules and biological systems 9 Molecules with flexible bonds 10 Silicate glasses and zeolites 11 Simple metals e g Al Ni Cu etc 1 2 2 Force Field The DL_POLY_2 force field includes the following features 1 All common forms of non bonded atom atom potential 2 Atom atom site site Coulombic potentials 3 Valence angle potentials OCCLRC 13 4 Dihedral angle potentials 5 Inversion potentials 6 Improper dihedral angle potentials 7 3 body valence angle and hydrogen bond potentials 8 4 body inversion potentials 9 Sutton Chen density dependent potentials for metals 6 The parameters describing these potentials may be obtained for example from the GROMOS 3 DREIDING 7 or AMBER 4 forcefield which share functional forms It is relatively easy to adapt DL POLY 2 to user specific force fields 1 2 8 Boundary Conditions DL POLY 2 will accommodate the following boundary conditions 1 None e g isolated polymer in space 2 Cubic periodic boundaries 3 Orthorhombic periodic boundaries 4 Parallelepiped periodic boundaries 5 Truncated octahedral periodic boundaries 6 Rhombic dodecahedral periodic boundaries 7 Slab x y periodic z nonperiodic 8 Hexagonal prism periodic
107. e The choice involves decisions about speed accuracy and memory requirements 3 point interpolation is the default option A utility program TABCHK is provided in the DL POLY utility sub directory to help users choose a sufficiently accurate interpolation scheme including array sizes for their needs 3 2 2 Assisting Compilation with the Utility Program PARSET A particular difficulty in creating a working version of DL POLY 2 prior to version 2 11 is creating the DL PARAMS INC file section 7 1 1 which specifies among other things the array sizes for the compiled code The copy of DL PARAMS INC supplied with DL_POLY_2 contains settings appropriate for the test cases and some of the benchmarks but is not guar anteed to be appropriate for any user s specific requirements Users must determine their own requirements and so produce their own version of DL PARAMS INO before compiling a working version While DL POLY 2 contains many error checks to prevent the arrays being exceeded during a run it is tedious to have to recompile the code each time an error is detected Furthermore the large number of parameters required to specify the entire code makes it very unlikely that the code will run successfully first time or even after several attempts To assist with this difficulty the utility program PARSET has been created section 6 1 1 It can be used to create a DL PARAMS INC file that is suitable for the simulation being attempted It work
108. e program if it can t identify any one of them from the atom types specified earlier in the file CCLRC 190 Action Correct the erroneous entry in the FIELD file and resubmit Message 85 error required velocities not in CONFIG file If the user attempts to start up a DL_POLY_2 simulation with the restart or restart scale directives see description of CONTROL file the program will expect the CONFIG file to contain atomic velocities as well as positions Termination results if these are not present Action Either replace the CONFIG file with one containing the velocities or if not available remove the restart directive altogether and let DL_POLY_2 create the velocities for itself Message 86 error calculated 3 body potential index too large DL_POLY_2 has a permitted maximum for the calculated index for any three body poten tial in the system i e as defined in the FIELD file If there are m distinct types of atom in the system the index can possibly range from 1 to m m 1 2 If the internally calculated index exceeds this number this error report results Action Standard user response Fix the parameter mxtbp Message 87 error too many link cells required in fbpfrc The FBPFRC subroutine uses link cells to compute the four body forces This message in dicates that the link cell arrays have insufficient size to work properly Action Standard user response Fix the parameter mxcell Message 89 erro
109. e DL_POLY_2 option to freeze the location of an atom i e hold it permanently in one position is not permitted for core shell units This includes freezing the core or the shell independently Action Remove the frozen atom option from the FIELD file Consider using a non polarisable atom instead Message 50 error too many bond angles specified DL_POLY_2 limits the number of valence angle potentials that can be specified in the FIELD file and checks for the violation of this Termination will result if the condition is violated Do not confuse this error with that described by message 51 below Action Standard user response Fix the parameter mxtang Message 51 error too many bond angles in system DL_POLY_2 limits the number of valence angle potentials in the system to be simulated actually the number to be processed by each node and checks for the violation of this Termination will result if the condition is violated Do not confuse this error with that described by message 50 above Action Standard user response Fix the parameter mxangl Consider the possibility that the wrong CONFIG file is being used e g similar system but larger size Message 52 error end of FIELD file encountered This message results when DL_POLY_2 reaches the end of the FIELD file without having read all the data it expects Probable causes missing data or incorrect specification of integers on the various directives Action Chec
110. e compiler concerned This is circumvented by compiling the offending subroutines unoptimised See the entries for various machines in the makefile to see how this is done if you experience problems with other subroutines 5 Changing the Timer The only other routine likely to cause problems is TIMCHK which requires a ma chine specific timer The makefile should select the appropriate timer for you but if the timer routine you require is not included you will need to add the appropriate lines of code TIMCHK returns the elapsed time in seconds Note that the C routine ETIME may be used on many unix systems It is used as the default timer by DL_POLY_2 on serial and PVM systems 6 Adding new functionality To include a new subroutine in the code simply add subroutine o to the list of object names in the makefile The simpliest way is to add names to the OBJ_ALL list 3 2 1 3 Note on Interpolation Schemes In DL_POLY_2 the short range Van der Waals contributions to energy and force are evaluated by interpolation of tables constructed at the beginning of execution DL_POLY_2 caters for three different interpolation schemes 3 point and 4 point in r space and linear interpolation in r space Tabulation in r avoids the use of the square root function in evaluation of the non bonded interactions and thus typically decreases execution time by 10 15 Note that tabulation in r usually requires more grid points and hence more memory th
111. e direct Coulomb sum there are likely to be problems of convergence DL POLY 2 will correctly handle the electrostatics of both molecular and atomic species However it is assumed that the system is electrically neutral A warning message is printed if the system is found to be charged but otherwise the simulation proceeds as normal No correction for non neutrality is applied 2 4 1 Atomistic and Charge Group Implementation The Ewald sum is an accurate method for summing long ranged potentials such as the Coulomb potential in periodic systems This can be a very cpu intensive calculation and the use of more efficient but less accurate methods is common Invariably this involves truncation of the potential at some finite distance freut If an atomistic scheme is used for the truncation criterion there is no guarantee that the interaction sphere will be neutral and spurious charging effects will almost certainly be seen in a simulation This arises 2Unlike the other elements of the force field the electrostatic forces are NOT specified in the input FIELD file but by setting appropriate directives in the CONTROL file See section 4 1 1 CCLRC 47 because the potential being truncated is long ranged 1 r for charge charge interactions However if the cutoff scheme is based on neutral groups of atoms then at worst at long distance the interaction will be a dipole dipole interaction and vary as 1 r The truncation effects at the cut
112. e example FIELD files in the data directory to see how typical FIELD files are constructed 4 1 3 3 Non bonded Interactions Non bonded interactions are identified by atom types as opposed to specific atomic indices The first type of non bonded potentials are the pair potentials The input of pair potential data is signalled by the directive vdw n CCLRC 120 where n is the number of pair potentials to be entered There follows n records each specifying a particular pair potential in the following manner atmnam 1 a8 first atom type atmnam 2 a8 second atom type key a4 1X potential key See table 4 12 variable 1 real potential parameter see table 4 12 variable 2 real potential parameter see table 4 12 variable 3 real potential parameter see table 4 12 variable 4 real potential parameter see table 4 12 variable 5 real potential parameter see table 4 12 The variables pertaining to each potential are described in table 4 12 Note that there is an empty column after the potential key This means that the potential paramaters are enterd in columns 22 to 81 Note that any pair potential not specified in the FIELD file will be assumed to be zero Note also that the Sutton Chen potential for metals is classified as a pair potential for input purposes The specification of three body potentials is initiated by the directive tbp n where n is the number of three body potentials to be entered There follows n records each specifying a pa
113. e first entry on a data record or line and which invoke a particular operation or provide numerical parameters Also associated with each directive may be one or more keywords which may qualify particular directive by for example adding extra options Directives can appear in any order in the CONTROL file except for the finish directive which marks the end of the file Some of the directives CCLRC 100 are mandatory for example the timestep directive that defines the timestep others are optional This way of constructing the file is very convenient but it has inherent dangers It is for example quite easy to specify the same directive more than once or specify contradictory directives or invoke algorithms that do not work together By and large DL_POLY_2 tries to sort out these difficulties and print helpful error messages but it does not claim to be foolproof Fortunately in most cases the CONTROL file will be small and easy to check visually It is important to think carefully about a simulation beforehand and ensure that DL_POLY_2 is being asked to do something that is physically reasonable It should also be remembered that the present capabilites the package may not allow the simulation required and it may be necessary for you yourself to add new features An example CONTROL file appears below The directives and keywords appearing are described in the following section Title Record Example CONTROL file for DL_POLY def
114. e number of link cells required for a given simulation exceeds the number allowed for by the DL POLY 2 arrays Action Standard user response Fix the parameter mxcell CCLRC 204 Message 394 error minimum image arrays exceeded The work arrays used in IMAGES have been exceeded Action Standard user response Fix the parameter mxxdf Message 396 error interpolation array exceeded DL_POLY_2 has sought to read past the end of an interpolation array This should never happen Action Contact the authors Message 398 error cutoff too small for rprim and delr This error can arise when the multiple timestep option is used It is essential that the primary cutoff rprim is less than the real space cutoff rcut by at least the Verlet shell width delr preferably much larger DL POLY 2 terminates the run if this condition is not satisfied Action Adjust rcut rprim and delr to satisfy the DL POLY 2 requirement These are defined with the directives cut prim and delr respectively Message 400 error rvdw greater than cutoff DL POLY 2 requires the real space cutoff rcut to be larger than or equal to the van der Waals cutoff rvdw and terminates the run if this condition is not satisfied Action Adjust rvdw and rcut to satisfy the DL POLY 2 requirement Message 402 error van der waals cutoff unset The user has not set a cutoff rvdw for the van der Waals potentials The simulation cannot proceed
115. e terms with the same Verlet neighbour list routines that are used to calculate the short range forces and EWALD3 calculates the self interac tion corrections It should be noted that the Ewald potential and force interpolation arrays in DL_POLY_2 are erc and fer respectively 2 4 6 Smooth Particle Mesh Ewald As its name implies the Smooth Particle Mesh Ewald SPME method is a modification of the standard Ewald method DL POLY 2 implements the SPME method of Essmann et al 31 Formally this method is capable of treating van der Waals forces also but in DL_POLY_2 it is confined to electrostatic forces only The main difference from the standard Ewald method is in its treatment of the the reciprocal space terms By means of an interpolation procedure involving complex B splines the sum in reciprocal space is represented on a three dimensional rectangular grid In this form the Fast Fourier Trans form FFT may be used to perform the primary mathematical operation which is a 3D convolution The efficiency of these procedures greatly reduces the cost of the reciprocal space sum when the range of k vectors is large The method briefly is as follows for full details see 31 1 Interpolation of the exp ik rj terms given here for one dimension exp 2riu k L b k 5 oo M uj Lexp 2nikl K 2 137 oo in which k is the integer index of the k vector in a principal direction K is the total number of grid points in
116. e that on record i only the atom name is mandatory any other items are not read by DL POLY 2 but may be added to aid alternative uses of the file for example the DL POLY 2 Graphical User Interface 20 4 1 2 3 Further Comments The CONFIG file has the same format as the output file REVCON section 4 2 3 When restarting from a previous run of DL POLY 2 i e using the restart or restart scale di rectives in the CONTROL file above the CONFIG file must be replaced by the REVCON file which is renamed as the CONFIG file The copy macro in the execute sub directory of DL POLY 2 does this for you OCCLRC 109 Table 4 5 CONFIG file key record 2 0 Coordinates included in file Coordinates and velocities included in file 2 Coordinates velocities and forces included in file Table 4 6 Periodic boundary key record 2 no periodic boundaries cubic boundary conditions orthorhombic boundary conditions parallelepiped boundary conditions truncated octahedral boundary conditions rhombic dodecahedral boundary conditions x y parallelogram boundary conditions with no periodicity in the z direction hexagonal prism boundary conditions CCLRC 110 4 1 3 The FIELD File The FIELD file contains the force field information defining the nature of the molecular forces It is read by the subroutine SYSDEF Excerpts from a force field file are shown below The example is the antibiotic Valinomycin in a cluster of 146 water molecule
117. ect n where n is test case number which ranges from 1 to 10 This macro sets up the required input files in the execute sub directory to run the n th test case 6 1 2 6 store The store macro provides a convenient way of moving data back from the execute sub directory to the data sub directory It invokes the unix commands CCLRC 149 mkdir data TEST 1 mv OUTPUT data TEST 1 0UTPUT mv REVCON data TEST 1 REVCON mv STATIS data TEST 1 STATIS mv REVIVE data TEST 1 REVIVE mv RDFDAT data TEST 1 RDFDAT mv ZDNDAT data TEST 1 ZDNDAT chmod 400 data TEST 1 which first creates a new DL POLY data TEST sub directory and then moves the stan dard DL_POLY output data files into it Store requires one argument store n where n is a unique string or number to label the output data in the data TES Tn sub directory Note that store sets the file access to read only This is to prevent the store macro overwriting existing data without your knowledge Chapter 7 DL POLY 2 Subroutines and Functions 150 CCLRC 151 Scope of Chapter This chapter describes all the subroutines of DL_POLY_2 to be found in the source subdi rectory A fuller description of the contents of the source sub directory is available in the DL_POLY_2 Reference Manual CCLRC 152 7 1 Subroutine and Function Specifications 7 1 1 DL_PARAMS INC The DL_POLY Parameters Include File 7 1 1 1 Header Cad ada ale ade ok ade ad ale
118. elaxation times ps ensemble nst hoover f fa select Hoover NaT ensemble with fi fa as the thermostat and barostat relaxation times ps ensemble pmf select NVE potential of mean force ensemble eps f set relative dielectric constant to f default 1 0 equil n equilibrate simulation for first n timesteps ewald precision f select Ewald sum for electrostatics with automatic parameter optimisation 0 f 5 ewald sum o k1 k2 k3 finish job time f mult n no elec no vdw pres f prim f select Ewald sum for electrostatics with o Ewald convergence parameter 1 k1 maximum k vector index in x direction k2 maximum k vector index in y direction k3 maximum k vector index in z direction close the CONTROL file last data record set job time to f seconds set multiple timestep multi step interval activated when n gt 2 ignore coulombic interactions ignore short range non bonded interactions set required system pressure to f k bars target pressure for constant pressure ensembles set primary cutoff to f A for multiple timestep algorithm only CCLRC print n print rdf quaternion f rdf f reaction restart restart scale scale n shake f shift spme precision f 103 print system data every n timesteps print radial distribution functions set quaternion tolerance to f default 1078 calculate radial distribution functions at intervals of f timesteps select reaction field ele
119. entre the HPCI Centre at Southampton and the CCP5 community We also thank users of previous versions of DL POLY who have passed on helpful comments CCLRC 4 Manual Notation In the DL_POLY Manual and Reference Manual specific fonts are used to convey specific meanings 1 2 directories indicates unix file directories ROUTINES indicates subroutines functions and programs macros indicates a macro file of unix commands directive indicates directives or keywords variables indicates named variables and parameters FILE indicates filenames Contents 1 Introduction 9 l l The DL POLY Packale iiris piaia a o ii RE eR 11 1 2 Eunctionalily se core ias ii A vau a S ue e 12 1 2 1 Molecular Systems 2 0 0000 eee eee es 12 12252 Force Field 4 26d p Noe eras fiat ee E VERSER ue 12 1 2 3 Boundary Conditions le 13 1 24 Algorithms sra hoes Be BG edunt et ace heh is eft 13 13 Programming Style es 15 1 3 4 Programming Language e 15 1 3 2 Memory Management lee 15 1 33 Target Computers llle 15 1 3 4 Version Control System CVS llle 16 1 8 5 Required Program Libraries lle 16 1 3 6 Internal Data Transfer ee 16 1 3 7 Internal Documentation lee 16 1 3 8 Subroutine Function Calling Sequences 17 1 3 9 FORTRAN Parameters ees 17 1 3 10 Arithmetic Precision 222A
120. er DFFTW MAKE LD mpxlf o LDFLAGS lesslp2 lfftw lrfftw L FFTW LIBRARY FC mpx1f FFLAGS c 03 NS2048 qarch pwr2 qnosave CPFLAGS D STRESS DMPI D POINTER integer DFFTW DESSL EX EX BINROOT BINROOT TYPE Cray t3e Manchester cray t3e dpp cp opt ct1 mpt mpt include mpif h mpif h MAKE FC f90 FFLAGS c dp 1mpi CPFLAGS Wp DCRAY DCRAY T3D D POINTER integer DSHMEM D STRESS P lowcase o MAKE LD f90 o FC 90 FFLAGS c dp lmpi LDFLAGS 1mpi CPFLAGS Wp DCRAY DCRAY T3D D POINTER integer DSHMEM D STRESS P TIMER EX EX BINROOT BINROOT TYPE Cray t3e Manchester with totalview flags cray t3e totalview dpp cp opt ctl mpt mpt include mpif h mpif h MAKE FC 90 FFLAGS c dp lmpi g X8 CPFLAGS Wp DCRAY DCRAY T3D D POINTER integer DSHMEM D STRESS P lowcase o MAKE LD f90 o FC 90 FFLAGS c dp lmpi g X8 LDFLAGS 1mpi g X8 CCLRC 163 CPFLAGS Wp DCRAY DCRAY_T3D D POINTER integer DSHMEM D STRESS P TIMER EX EX BINROOT BINROOT TYPE ray t3e serial cray t3e serial dpp MAKE LD f90 o LDFLAGS FC f90 FFLAGS c dp 03 aggress unroll2 nojump TIMER A CPFLAGS D STRESS DSERIAL P D POINTER intger V EX
121. ermitted values Periodic boundary key See table 4 6 for permitted values omitted if imcon 0 O 000000000000000 O 000000000000000 7 274585343 0 7702718106 4432 030587 7 340573742 4 328786484 1255 814536 7 491549620 2 951142896 2379 766752 3 732081894 0 5473436377 5365 202509 x component of a cell vector CCLRC 108 ce11 2 real y component of a cell vector cel11 3 real z component of a cell vector record 4 omitted if imcon 0 cell 4 real x component of b cell vector cell 5 real y component of 6 cell vector cel1 6 real z component of b cell vector record 5 omitted if imcon 0 cell 7 real x component of c cell vector cell 8 real y component of c cell vector cell 9 real z component of c cell vector Subsequent records consists of blocks of between 2 and 4 records depending on the value of the levcfg variable Each block refers to one atom The atoms must be listed sequentially in order of increasing index Within each block the data are as follows record i atmnam a8 atom name index integer atom index atmnum integer atomic number record ii XXX real x coordinate yyy real y coordinate ZZZ real z coordinate record iii included only if levcfg gt 0 VXX real x component of velocity vyy real y component of velocity VZZ real x component of velocity record iv included only if levcfg gt 1 fxx real x component of force fyy real y component of force fzz real z component of force Not
122. esired tolerance the correction calculation is repeated 4 Steps 2 and 3 are repeated until all bondlengths satisfy the convergence criterion This iteration constitutes stage 2 of the SHAKE algorithm The parallel version of this algorithm as implemented in DL_POLY_2 is known as RD SHAKE 9 see section 2 6 8 The subroutine NVE_1 implements the Verlet leapfrog algorithm with bond constraints The routine RDSHAKE_1 is called to apply the SHAKE corrections to position It should be noted that the fully converged constraint forces G make a contribution to the system virial and the stress tensor The contribution to be added to the atomic virial for each constrained bond is The contribution to be added to the atomic stress tensor is given by 0 dct 2 162 where q and f indicate the x y z components The atomic stress tensor derived from the pair forces is symmetric 2 5 2 Potential of Mean Force PMF Constraints and the Evaluation of Free Energy A generalization of bond constraints can be made to constrain a system to some point along a reaction coordinate A simple example of such a reaction coordinate would be the distance between two ions in solution If a number of simulations are conducted with the system constrained to different points along the reaction coordinate then the mean constraint force may be plotted as a function of reaction coordinate and the function integrated to obtain the free energy for the overall proc
123. ess 35 The PMF constraint force virial and contributions to the stress tensor are obtained in a manner analagous to that for a bond constraint see previous section The only difference is that the constraint is now applied between the centres of two groups which need not be atoms alone DL_POLY_2 reports the PMF constraint virial W for each simulation Users can convert this to the PMF constraint force from Gpwur Wenmr deur where dpyp is the constraint distance between the two groups used to define the reaction coordinate CCLRC 60 2 5 3 Thermostats The system may be coupled to a heat bath to ensure that the average system temperature is maintained close to the requested temperature Text When this is done the equations of motion are modified and the system no longer samples the microcanonical ensemble Instead trajectories in the canonical NVT ensemble or something close to it are generated DL_POLY_2 comes with three different thermostats Nos Hoover 16 Berendsen 14 and Gaussian constraints 15 Of these only the Nos Hoover algorithm generates trajectories in the canonical NVT ensemble The other methods will produce properties that typically differ from canonical averages by O 1 N 10 2 5 3 1 Nos Hoover Thermostat In the Nos Hoover algorithm 16 Newton s equations of motion are modified to read dr t _ x Wb aul _ I x v 2 2 163 2 164 The friction coefficient x is c
124. etimes print warning mes sages These indicate that the code has detected something that is unusual or inconsistent The detection is non fatal but the user should make sure that the warning does represent a harmless condition CCLRC 19 1 4 The DL_POLY_2 Directory Structure The entire DL_POLY_2 package is stored in a Unix directory structure The topmost directory is named dl_poly_nn where nn is a generation number Beneath this directory are several sub directories named source utility data bench execute build public respa and sdk Briefly the content of each sub directory is as follows sub directory contents source primary subroutines for the DL_POLY_2 package utility subroutines programs and example data for all utilities data example input and output files for DL_POLY_2 bench large test cases suitable for benchmarking execute the DL POLY 2 run time directory build makefiles to assemble and compile DL POLY 2 programs public directory of routines donated by DL_POLY_2 users sdk directory of routines used to construct the DL POLY 2 GUI respa directory of routines used to construct the DL POLY 2 RESPA program A more detailed description of each sub directory follows 1 4 1 The source Sub directory In this sub directory all the essential source code for DL_POLY_2 excluding the utility software In keeping with the package concept of DL_POLY_2 it does not contain any complete programs these are assemble
125. etween nodes Each node is responsible for a unique set of nonbonded interactions and the neighbour list is therefore different on each node DL_POLY_2 uses a method based on the Brode Ahlrichs scheme 22 see figure below to construct the neighbour list CCLRC 74 Additional modifications are necessary to handle the excluded atoms 42 A distributed excluded atoms list is constructed by DL POLY 2 at the start of the simulation The list is constructed so that the excluded atoms are referenced in the same order as they would appear in the Verlet neighbour list if the bonded interactions were ignored allowing for the distributed structure of the neighbour list Brode Ahlrichs Algorithm 12 Atoms 4 processors Processor 0 10 11 10 12 10 1 10 2 10 3 11 12 11 1 11 2 11 3 11 4 12 1 12 2 12 3 12 4 12 5 Schematic diagram of the parallel implementation of the Brode Ahlrichs algorithm The diagram illustrates the reordering of the upper triangular matrix of n n 1 2 pair interactions so that the rows of the matrix are of approximately equally length Each entry in the table consists of a primary atom index constant within a row and a neighbouring atom index Rows are assigned sequentially to nodes In the diagram node 0 deals with rows 1 5 and 9 node 1 to rows 2 6 and 10 etc When a charge group scheme as opposed to an atomistic scheme is used for the non bonded terms the group group interactions are distributed using the B
126. f90 LDFLAGS 1mpi TIMER FFLAGS c Ofast 64 CPFLAGS D STRESS DMPI DCRAY D POINTER integer EX EX BINROOT BINROOT TYPE Silicon Graphics Origin 2000 parallel SHMEM sg2k shmem dpp cp usr include mpif h mpif h MAKE LD f90 o FC f90 FFLAGS c 64 mips4 fast ip27 IPA OPT Olimit 0 LDFLAGS 64 mips4 fast ip27 IPA OPT Olimit 0 1sma lmpi lblas OBJ_EXT gsync o mynode o nodedim o numnodes o TIMER CPFLAGS DMPI D STRESS DSGI 02K DCRAY D POINTER integer EX EX BINROOT BINROOT TYPE Sg2k dpp MAKE LD 90 o LDFLAGS n32 mips4 FC f90 FFLAGS c 03 G O mips4 r10000 c r8 n32 TIMER OBJ_SPME N CPFLAGS D STRESS DSERIAL D POINTER integer CFLAGS c 03 n32 mips4 r10000 EX EX BINROOT BINROOT TYPE Silicon Graphics Origin 2000 serial Irix 6 5 no SPME sg2k 16 5 dpp MAKE LD f90 o LDFLAGS n32 mips4 IPA FC f90 FFLAGS c n32 mips4 fast ip27 LNO fusion 2 A TIMER OBJ_SPME CPFLAGS D STRESS DSERIAL D POINTER integer CFLAGS c 03 n32 mips4 r10000 EX EX BINROOT BINROOT TYPE CCLRC 167 Silicon Graphics 02 R5k serial no SPME sg2 r5k dpp MAKE LD f90 o LDFLAGS n32 mips4 A FC f90 FFLAGS c 03 G O mips4 r5000 c r8 n32 N TIMER QBJ SPME CPFLAGS D STRE
127. fftw echo beowulf absoft echo cray t3e echo cray t3e serial echo cray t3e totalview echo dec alpha echo dec alpha ev6 echo exemplar echo hitachi sr2201 echo hp echo hp c240 echo intel echo linux echo pentium absoft echo pentium portland echo rs6k echo rs6k pwr3 Cecho sgi0k echo sgi0k fftw echo sg2 rbk echo sg2k Cecho sg2k i6 5 echo sg2k shmem echo sg8k mpi echo sg8k mpi f echo sp2 mpi echo sp2 mpi debug echo sp2 mpi fftw echo sun echo sun ultra echo L Cecho Please examine Makefile for details sp2 mpi dpp CCLRC 162 cp usr lpp ppe poe include mpif h mpif h MAKE FC mpx1f FFLAGS c NS2048 qarch pwr2 qnosave CPFLAGS D STRESS DMPI DESSL D POINTER integer intlist o MAKE LD mpxlf o LDFLAGS lesslp2 FC mpx1f FFLAGS c 03 NS2048 qarch pwr2 qnosave CPFLAGS D STRESS DMPI DESSL D POINTER integer EX EX BINROOT BINROOT TYPE sp2 mpi debug dpp cp usr lpp ppe poe include mpif h mpif h MAKE LD mpxlf o LDFLAGS lesslp2 FC mpxlf FFLAGS g c C NS2048 qarch pwr2 qnosave CPFLAGS D STRESS DMPI DESSL D POINTER integer EX EX BINROOT BINROOT TYPE sp2 mpi fftw dpp cp usr lpp ppe poe include mpif h mpif h MAKE FC mpx1f FFLAGS c NS2048 qarch pwr2 qnosave CPFLAGS D STRESS DMPI D POINTER integ
128. function arguments are scalars With this reduction the force on an atom derived from the valence angle potential is given by O ft apa O Bj ri Tik 2 22 CCLRC 31 with atomic label being one of i j k and o indicating the x y z component The derivative is 9 a ara U Cue ras na S ris rit AO r9 0 ZA Ojik S rir 02 6 ar is re 0 A 0jix S rij Bu 96 25 S rix 2 23 Tik Orik with dg 1 if a b and 6g 0 if a Z b In the absence of screening terms S r this formula reduces to o o grg U Oii ri Min Beg Ok 2 24 The derivative of the angular function is 0 1 o Jefa Lc AB mec Alli E E 2 25 Ore jik E 00 jy jik Or TijTik with O Tij Lik T ri 4 h g i gy gj ore Tijfik g m a oem cos 0jix 4 Se Sea dek 0n 3 2 26 Tij Tik The atomic forces are then completely specified by the derivatives of the particular functions A and S r The contribution to be added to the atomic virial is given by W rij f t rix fy 2 27 It is worth noting that in the absence of screening terms S r the virial is zero 26 The contribution to be added to the atomic stress tensor is given by oe 18 f ro fe 2 28 and the stress tensor is symmetric In DL POLY 2 valence forces are handled by the routine ANGFRC 2 2 4 Angular Restraints In DL_POLY_2 angle restraints in which the angle
129. g is the distance of the atom from its position at t 0 1 harmonic potential harm 1 U rio ah r 2 63 2 restrained harmonic rhrm 1 2 U rio gru Tio Te 2 64 1 U ri are kre rio Te Ti gt Te 2 65 3 Quartic potential quar k k k U rio 5 ri 3 rio T r 2 66 The force on the atom 4 arising from a tether potential is obtained using the general formula atto Lio 2 67 The contribution to be added to the atomic virial is given by E Tio W rio f 2 68 CCLRC 39 The contribution to be added to the atomic stress tensor is given by gor Sey 2 69 where o and f indicate the x y z components The atomic stress tensor derived in this way is symmetric In DL_POLY_2 bond forces are handled by the routine TETHFRC 2 2 9 Frozen Atoms DL_POLY_2 also allows atoms to be completely immobilised i e frozen at a fixed point in the MD cell This is achieved by setting all forces and velocities associated with that atom to zero during each MD timestep Frozen atoms are signalled by assigning an atom a non zero value for the freeze parameter in the FIELD file DL_POLY_2 does not calculate contributions to the virial or the stress tensor arising from the constraints required to freeze atomic positions In DL_POLY_2 the frozen atom option cannot be used for sites in a rigid body As with the tethering potential the reference position is scaled with the cell vectors in con
130. gorithm is implemented in NPT_B1 with 4 or 5 iterations used to obtain self consistency in the v t Cell size and shape variations The extension of the isotropic algorithm to anisotropic cell variations is straightforward The tensor 7 is defined by At n 1 PE pid g 2 184 and the new cell vectors given by H t At H t n 2 185 As in the isotropic case the Berendsen thermostat is applied simultaneously and 4 or 5 itera tions are used to obtain convergence The algorithm is implemented in NST B nonbonded systems and NPT_B3 with bond constraints 2 5 6 Rigid Bodies and Rotational Integration Algorithms 2 5 6 1 Description of Rigid Body Units A rigid body unit is a collection of point atoms whose local geometry is time invariant One way to enforce this in a simulation is to impose a sufficient number of bond constraints between the atoms in the unit However in many cases this is may be either problematic or impossible Examples in which it is impossible to specify sufficient bond constraints are 1 linear molecules with more than 2 atoms e g CO2 2 planar molecules with more than three atoms e g benzene CCLRC 66 Even when the structure can be defined by bond constraints the network of bonds produced may be problematic Normally they make the iterative SHAKE procedure slow particu larly if a ring of constraints is involved as occurs when one defines water as a constrained triangle It is also possible
131. h D the cell vectors appearing in the CONFIG file should be D 0 0 0 D 0 0 0 D Note the origin of the atomic coordinates is the centre of the cell The cubic boundary condition can be used with the Ewald summation method Orthorhombic periodic boundaries IMCON 2 The orthorhombic cell is also a common periodic boundary which closely resembles the cubic cell in use In DL_POLY_2 the cell is defined with principle axes passing through the centres of the faces For an orthorhombic cell with sidelengths D in X direction E in Y direction and F in Z direction the cell vectors appearing in the CONFIG file should be D 0 0 0 E 0 0 0 F Note the origin of the atomic coordinates is the centre of the cell The orthorhombic boundary condition can be used with the Ewald summation method CCLRC 172 The orthorhomic MD cell Parallelepiped periodic boundaries IMCON 3 A The parallelepiped MD cell The parallelepiped e g monoclinic or triclinic cell is generally used in simulations of crystalline materials where its shape and dimension is commensurate with the unit cell of the crystal Thus for a unit cell specified by three principal vectors a b c the MD cell is defined in the DL_POLY_2 CONFIG file by the vectors La La2 Laz Mb Mb2 Mb3 Nc Mc2 Nc3 in which L M N are integers reflecting the multiplication of the unit cell in each principal direction Note that the atomic coor
132. he cell volume the ratio is about 74 to 68 The principal axis in the X direction of the rhombic dodecahedron passes through the centre of the cell and the centre of a rhombic face The Y axis does likewise but is set at 90 degrees to the X axis The Z axis completes the orthonormal set and passes through a vertex where four faces meet If the width D of the cell is defined as the perpendicular distance between two opposite faces the cell vectors required for the DL_POLY_2 CONFIG file are D 0 0 0 D 0 0 0 2D These also define the enscribing orthorhombic cell which has twice the MD cell volume In DL POLY 2 the centre of the cell is also the origin of the atomic coordinates The rhombic dodecahedron can be used with the Ewald summation method CCLRC 174 The rhombic dodecahedral MD cell Slab boundary conditions IMCON 6 Slab boundaries are periodic in the X and Y directions but not in the Z direction They are particularly useful for simulating surfaces The periodic cell in the XY plane can be any parallelogram The origin of the X Y atomic coordinates lies on an axis perpendicular to the centre of the parallelogram The origin of the Z coordinate is where the user specifies it but at or near the surface is recommended If the XY parallelogram is defined by vectors A and B the vectors required in the CONFIG file are A1 A2 0 B1 B2 0 0 0 D where D is any real number including zero If D is nonzero it will be u
133. he contribution to be added to the atomic virial is given by 4 W Y rn f 2 61 i 1 CCLRC 38 However it is possible to show by thermodynamic arguments cf 26 or simply from the fact that the sum of forces on atoms j k and n is equal and opposite to the force on atom i that the inversion potential makes no contribution to the atomic virial If the force components f for atoms i j k n are calculated using the above formu lae it is easily seen that the contribution to be added to the atomic stress tensor is given by o 0 fF 9G fF re f 2 62 The sum of the diagonal elements of the stress tensor is zero since the virial is zero and the matrix is symmetric In DL_POLY_2 inversion forces are handled by the routine INVFRC 2 2 8 Tethering Forces DL_POLY_2 also allows atomic sites to be tethered to a fixed point in space rp taken as their position at the beginning of the simulation This is also known as position restraining The specification which comes as part of the molecular description requires a tether potential type and the associated interaction parameters Note firstly that application of tethering potentials means that momentum will no longer be a conserved quantity of the simulation Secondly in constant pressure simulations where the MD cell changes size or shape the reference position is scaled with the cell vectors The potential functions available in DL_POLY_2 are as follows in each case rj
134. his error arises when there are no VDW potentials specified in the FIELD file but the user has not specified no vdw in the CONTROL file In other words DL_POLY_2 expects the FIELD file to contain VDW potential specifications Action Edit the FIELD file to insert the required potentials or specify no vdw in the CONTROL file Message 150 error unknown van der waals potential selected DL_POLY_2 checks when constructing the interpolation tables for the short ranged poten tials that the potential function requested is one which is of a form known to the program CCLRC 196 If the requested potential form is unknown termination of the program results The most probable cause of this is the incorrect choice of the potential keyword in the FIELD file or one in the wrong columns input is formatted Action Read the DL_POLY_2 documentation and find the potential keyword for the potential desired Insert the correct index in the FIELD file definition and ensure it occurs in the correct columns 17 20 If the correct form is not available look at the subroutine FORGEN or its variant and define the potential for yourself It is easily done Message 151 error unknown metal potential selected The metal potentials available in DL_POLY_2 are confined to density dependent forms of the Sutton Chen type This error results if the user attempts to specify another Action Re specify the potential as Sutton Chen type if possible Check the p
135. his is not an option investigate the possibility of increasing the heap size for your application Talk to your systems support people for advice on how to do this Message 35 error logical array memory allocation failure DL_POLY_2 has failed to allocate sufficient memory to accommodate one or more of the logical arrays in the code Action This may simply mean that your simulation is too large for the machine you are running on Consider this before wasting time trying a fix Try using more processing nodes if they are available If this is not an option investigate the possibility of increasing the heap size for your application Talk to your systems support people for advice on how to do this Message 40 error too many bond constraints specified DL_POLY_2 sets a limit on the number of bond constraints that can be specified in the FIELD file Termination results if this number is exceeded See FIELD file documentation Do not confuse this error with that described by message 41 below Action Standard user response Fix the parameter mxtcon Message 41 error too many bond constraints in system DL_POLY_2 sets a limit on the number of bond constraints in the simulated system as a whole This number is a combination of the number of molecules and the number of per molecule divided by the number of processing nodes Termination results if this number is exceeded Do not confuse this error with that described by message 40 abov
136. his sub directory if they wish to use DL_POLY_2 as intended The experienced user is not absolutely required to use DL_POLY_2 this way however 1 4 6 The build Sub directory This sub directory contains the standard makefiles for the creation i e compilation and linking of the DL_POLY_2 simulation programs The makefiles supplied select the appro priate subroutines from the source sub directory and deposit the executable program in the execute directory The user is advised to copy the appropriate makefile into the source directory in case any modifications are required The copy in the build sub directory will then serve as a backup 1 4 7 The public Sub directory This sub directory contains assorted routines donated by DL_POLY users Potential users should note that these routines are unsupported and come without any guarantee or liability whatsoever They should be regarded as potentially useful resources to be hacked into shape as needed by the user This directory is available from the CCP5 Program Library by direct FTP see below 1 4 8 The respa Sub directory This sub directory first appeared in Version 2 12 when the RESPA subroutines were sep arated from the source directory to make construction of the RESPA program simpler The respa sub directory consists of the subroutines unique to the RESPA application The RESPA makefile Makefile_respa in the build sub directory has been designed to gather the additional subroutines requi
137. hm F Acos 2nr z Lz 2 107 3 Continuous shear shrx 1 U tal z gt zo 2 108 4 Gravitational field grav Fi Fi mH 2 109 5 Magnetic field magn i Fi qi vi A H 2 110 6 Containing sphere sphr OCCLRC 46 It is recommended that the use of an external field should be accompanied by a thermostat this does not apply to example 6 since this is a conservative field In DL POLY 2 external field forces are handled by the routine EXTNFLD 2 4 Long Ranged Electrostatic Coulombic Potentials DL POLY 2 incorporates several techniques for dealing with long ranged electrostatic po tentials These are as follows 1 Atomistic and charge group implementation 2 Direct Coulomb sum 3 Truncated and shifted Coulomb sum 4 Coulomb sum with distance dependent dielectric 5 Ewald sum 6 Smooth Particle Mesh Ewald SPME 7 Reaction field 8 Dynamical shell model Some of these techniques can be combined For example 1 3 and 4 can be used in con junction with 7 The Ewald sum and SPME are restricted to periodic or pseudo periodic systems only though DL_POLY_2 can handle a broad selection of periodic boundary condi tions including cubic orthorhombic parallelepiped truncated octahedral hexagonal prism and rhombic dodecahedral The Ewald sum is the method of choice for periodic systems The other techniques can be used with either periodic or non periodic systems though in the case of th
138. hose obtained in this prescription since they specify a cubic lattice not a radius of convergence CCLRC 95 to solve recursively for a using equation 3 1 to give the first guess The relative error in the reciprocal space term is approximately amp exp k2 407 zu 3 3 where 9 kmas T kmax 3 4 is the largest k vector considered in reciprocal space L is the width of the cell in the specified direction and kmax is an integer For a relative error of 4 x 107 this means using kmar Y 6 20 kmax is then kmax gt 3 2 L Teut 3 5 In a cubic system Teut L 2 implies kmax 7 In practice the above equation slightly over estimates the value of kmax required so optimal values need to be found experimentally In the above example kmax 5 or 6 would be adequate If your simulation cell is a truncated octahedron or a rhombic dodecahedron then the estimates for the kmax need to be multiplied by 21 3 This arises because twice the normal number of k vectors are required half of which are redundant by symmetry for these boundary contributions 30 If you wish to set the Ewald parameters manually via the ewald sum or spme sum directives the recommended approach is as follows Preselect the value of reut choose a working a value of a of about 3 2 Tcy and a large value for the kmax say 10 10 10 or more Then do a series of ten or so single step simulations with your initial configuration and with o ranging over the value
139. iables 1 5 functional form 12 6 B U r 4 4 Lennard Jones o U r 4e Io 7 2 n m ro U r 237 m C2 n 2 7 Buckingham pC U r A exp 5 Born Huggins Blo C D U r A exp B o r S E Meyer 12 10 H bond B U r st 5 Shifted force n m ro ret U r D A n m enm pun te Y nm fee G e n m OS Sutton Chen a nim Cc U r e OH Syml pi Es 55 Tabulation tabulated potential Note in this formula the terms o f and y are compound expressions involving the variables E n m ro and re See section 2 3 1 for further details Note re defaults to the general van der Waals cutoff rvdw or rcut if it is set to zero or not specified or not specified in the FIELD file CCLRC 136 Table 4 13 Three body potentials potential type Variables 1 4 functional formt Truncated harmonic U 0 E 0 00 exp ri F T P Screened harmonic U 0 0 69 exp rij 1 rix p Screened Vessal 24 O SU 1 00 r 0 m7 exp rij p1 Ti p2 Truncated Vessal 25 U 0 k 9 9 09 0 00 2x 57 9 69 x 69 exp r5 73 0 hbnd H bond 7 U 8 Dyycos 0 5 Rpy rjx 2 6 Rns 7 5k 10 is the a b c angle Table 4 14 Four body Potentials potential type Variables 1 2 functional formt Harmonic Harmonic cosine Planar 1 is the inversion angle OCCLRC 137 Table 4 15 External field
140. icant modification 30 The RD strategy is applied to complex molecular systems as follows 1 Using the known atomic coordinates r each node calculates a subset of the forces acting between the atoms These are usually comprised of a b atom atom pair forces e g Lennard Jones Coulombic etc c valence angle forces non rigid atom atom bonds d e 2 The computed forces are accumulated in incomplete atomic force arrays f inde pendently on each node dihedral angle forces improper dihedral angle forces CCLRC 73 3 The atomic force arrays are summed globally over all nodes 4 The complete force arrays are used to update the atomic velocities and positions It is important to note that load balancing i e equal and concurrent use of all processors is an essential requirement of the overall algorithm In DL_POLY_2 this is accomplished for the pair forces with an adaptation of the Brode Ahlrichs scheme 22 2 6 2 Distributing the Intramolecular Bonded Terms DL_POLY_2 handles the intramolecular in which the atoms involved in any given bond term are explicitly listed Distribution of the forces calculations is accomplished by the following scheme 1 Every atom in the simulated system is assigned a unique index number from 1 to N 2 Every intramolecular bonded term Utype in the system has a unique index number itype from 1 to Niype where type represents a bond angle or dihedral 3
141. ifi cation of the file e The last record is a finish directive which marks the end of the input data Between the header and the finish directive a wide choice of control directives may be inserted These are described below 4 1 1 2 The CONTROL File Directives The directives available are as follows directive meaning all pairs use all pairs for electrostatic calculations cap f cap forces during equilibration period fis maximum cap in units of kT A default f 1000 close time f set job closure time to f seconds collect include equilibration data in overall statistics coul calculate coulombic forces cut f set required forces cutoff to f CCLRC 102 distan calculate coulombic forces using distance dependent dielectric delr f set Verlet neighbour list shell width to f A ensemble nve select NVE ensemble default ensemble nvt ber f select NVT ensemble with Berendsen thermostat with relaxation constant f ps ensemble nvt evans select NVT ensemble with Evans thermostat ensemble nvt hoover f select NVT ensemble with Hoover Nose thermostat with relaxation constant f ps ensemble npt ber fi fa select Berendsen NPT ensemble with fi fa as the thermostat and barostat relaxation times ps ensemble npt hoover f f select Hoover NPT ensemble with fi fa as the thermostat and barostat relaxation times ps ensemble nst ber f fa select Berendsen NaT ensemble with fi fo as the thermostat and barostat r
142. igure your simulation to an appropriate boundary condition Message 80 error too many pair potentials specified DL_POLY_2 places a limit on the number of pair potentials that can be specified in the FIELD file Exceeding this number results in termination of the program execution Action Standard user response Fix the parameters mxsvdw and mxvdw Message 81 error unidentified atom in pair potential list DL POLY 2 checks all the pair potentials specified in the FIELD file and terminates the program if it can t identify any one of them from the atom types specified earlier in the file Action Correct the erroneous entry in the FIELD file and resubmit Message 82 error calculated pair potential index too large In checking the pair potentials specified in the FIELD file DL POLY 2 calculates a unique integer index that henceforth identifies the potential within the program If this index becomes too large termination of the program results Action Standard user response Fix the parameters mxsvdw and mxvdw Message 83 error too many three body potentials specified DL POLY 2 has a limit on the number of three body potentials that can be defined in the FIELD file This error results if too many are included Action Standard user response Fix the parameter mxtbp Message 84 error unidentified atom in 3 body potential list DL POLY 2 checks all the 3 body potentials specified in the FIELD file and terminates th
143. iles will then need to be edited to account for the solvent molecules added to the file Hint to save yourself some work in entering the non bonded interactions variables involving solvent sites to the FIELD file put two bogus atoms of each solvent type at the end of the CONNECT DAT file for AMBER force fields the utility AMBFORCE will then evaluate all the non bonded variables required by DL_POLY_2 Remember to delete the bogus entries from the CONFIG file before running DL POLY 2 3 3 4 Analysing Results DL_POLY_2 is not designed to calculate every conceivable property you might wish from a simulation Apart from some obvious thermodynamic quantities and radial distribution functions it does not calculate anything beyond the atomic trajectories on line You must therefore be prepared to post process the HISTORY file if you want other information There are some utilities in the DL POLY 2 package to help with this but the list is far from exhaustive In time we hope to have many more Our users are invited to submit code to the DL POLY 2 public library to help with this The utilities available are described in the DL POLY 2 Reference Manual 6 Users should also be aware that many of these utilities are incorporated into the DL_POLY_2 Graphical User Interface 20 3 3 5 Choosing Ewald Sum Variables This section outlines how to optimise the accuracy of the Ewald sum parameters for a given simulation In what follows the directive spme
144. ilibrium Message 330 error mxewld parameter incorrect DL_POLY_2 has two strategies for parallelization of the reciprocal space part of the Ewald sum If EWALD1 is used the parameter mxewld should equal the parameter msatms If EWALD 1A is used this parameter should equal mxatms Action Standard user response Set the parameter mxewld to the value appropriate for the version of EWALD1 you are using Recompile the program Message 340 error invalid integration option requested DL_POLY_2 has detected an incompatibility in the simulation instructions namely that the requested integration algorithm is not compatible with the physical model It may be possible to override this error trap but it is up to the user to establish if this is sensible Action This is a non recoverable error unless the user chooses to override the restriction Message 350 error too few degrees of freedom This error can arise if a small system is being simulated and the number of constraints applied is too large Action Simulate a larger system or reduce the number of constraints Message 360 error frozen atom found in rigid body DL_POLY_2 does not permit a site in a rigid body to be frozen i e fixed in one location in space Action Remove the freeze condition from the site concerned Consider using a very high site mass to achieve a similar effect Message 380 error simulation temperature not specified DL_POLY_2 has failed
145. in this operation may be exceeded resulting in termination of the program Action Standard user response Fix the parameter mxexcl Message 67 error incorrect boundary condition in thbfre Three body forces in DL_POLY_2 are only permissible with cubic orthorhombic and par allelepiped periodic boundaries Use of other boundary conditions results in this error Action If nonperiodic boundaries are required the only option is to use a very large simulation cell with the required system at the centre surrounded by a vacuum This is not very efficient however and use of a realistic periodic system is the best option Message 69 error too many link cells required in thbfrc The calculation of three body forces in DL_POLY_2 is handled by the link cell algorithm This error arises if the required number of link cells exceeds the permitted array dimension in the code Action Standard user response Fix the parameter mxcell CCLRC 188 Message 70 error constraint bond quench failure When a simulation with bond constraints is started DL_POLY_2 attempts to extract the kinetic energy of the constrained atom atom bonds arising from the assignment of initial random velocities If this procedure fails the program will terminate The likely cause is a badly generated initial configuration Action Some help may be gained from increasing the cycle limit by following the standard user response to increase the control parameter
146. ine the state point temperature 300 0 simulation length and equilibration steps 2000 equilibration steps 1000 scale every 5 steps timestep 0 0005 ps multiple timestep 1 steps specify cutoffs cutoff delr print controller print every rdf options rdf sampling every print rdf 7 6 angstrom 0 5 angstrom 100 steps 10 steps job time and permitted wind up time job time close time forces options ewald sum 21000 seconds 200 seconds 0 48 6 6 6 cap forces in equilibration mode 2000 kT A CCLRC 101 ensemble options ensemble nve default option statistics controls stats every 2000 steps stack 100 deep trajectory dumping controls trajectory nstraj 1 istraj 50 keytrj 0 finish 4 1 1 1 The CONTROL file format The file is free formatted integers reals and additional keywords are entered following the directive on each record Real and integer numbers must be separated by a non numeric character preferably a space or comma to be correctly interpreted No logical variables appear in the control file Comment records beginning with a and blank lines may be added to aid legibility see example above Additional annotation may be added onto the directive line provided it does not contain numerical characters or appear where a directive or keyword is expected The CONTROL file is not case sensitive e The first record in the CONTROL file is a header 80 characters long to aid ident
147. ion The DL_POLY_2 RESPA Program is a variant of DL_POLY_2 that handles the time re versible multiple timestep RESPA algorithm due to Tuckerman and Berne 17 18 as im plemented by Procacci and Marchi for atomic and rigid ion systems 19 However it is not applicable to systems which have rigid body molecules or constraints and for this reason the RESPA code is kept separate from the DL_POLY_2 main source in the sub directory called respa The DL_POLY_2 implementation allows the user to define three concentric regions around a given atom Forces deriving from atoms in the innermost region are updated more frequently i e every timestep than those in the immediate outer region which in turn are updated more frequently than those deriving from the outermost region This depending on the relative sizes of each region and the frequency of the forces update OCCLRC 72 can represent a great computational saving This is coupled with the advantage that the algorithm is time reversible and therefore possesses long term stability The method is fully documented in 19 A makefile Makefile respa is available in the build sub directory which will build the RESPA program DLRESPA X A test case may be found in the data sub directory 2 6 DL POLY Parallelisation DL POLY 2 is a distributed parallel molecular dynamics package based on the Replicated Data parallelisation strategy 41 42 In this section we briefly outline the basic method ol
148. ion cell For timesteps greater than nstraj the HISTORY file is appended at intervals speci fied by the traj directive in the CONTROL file with the following information for each configuration record i a8 4110 f12 6 timestep a8 the character string timestep nstep integer the current time step natms integer number of atoms in configuration keytrj integer trajectory key again CCLRC imcon integer tstep real record ii 3g12 4 for imcon gt 0 cell 1 real cel1 2 real ce11 3 real record iii 3g12 4 for imcon 0 cell1 4 real cell 5 real cel1 6 real record iv 3g12 4 for imcon gt 0 cell 7 real cell 8 real cel1 9 real 126 periodic boundary key again integration timestep x component of a cell vector y component of a cell vector z component of a cell vector x component of b cell vector y component of b cell vector z component of b cell vector x component of c cell vector y component of c cell vector z component of c cell vector This is followed by the configuration for the currect timestep i e for each atom in the system the following data are included record a a8 i10 2f12 6 atmnam as iatm i10 weight f12 6 charge 112 6 record b 3e12 4 XXX real yyy real ZZZ real record c 3e12 4 only for keytrj gt 0 VXX real vyy real VZZ real record d 3e12 4 only for keytrj gt 1 fxx real fyy real fzz real atomic label atom index atomic mass a m u atomic charge e
149. is now short ranged and treatable by the methods described above section 2 1 The second modification is to superimpose a second set of gaussian charges this time with the same charges as the original point ions and again centred on the point ions so nullifying the effect of the first set of gaussians The potential due to these gaussians is obtained from Poisson s equation and is solved as a Fourier series in Reciprocal Space The complete Ewald sum requires an additional correction known as the self energy correction which arises from a gaussian acting on its own site and is constant Ewald s method therefore replaces a potentially infinite sum in real space by two finite sums one in real space and one in reciprocal space and the self energy correction For molecular systems as opposed to systems comprised simply of point ions additional modifications are necessary to correct for the excluded intra molecular Coulombic inter actions In the real space sum these are simply omitted In reciprocal space however the effects of individual gaussian charges cannot easily be extracted and the correction is made in real space It amounts to removing terms corresponding to the potential energy of an ion due to the gaussian charge on a neighbouring charge m or vice versa This correction appears as the final term in the full Ewald formula below The distinction between the error function er f and the more usual complementary error function e
150. k FIELD file for missing or incorrect data and correct Message 53 error end of CONTROL file encountered This message results when DL_POLY_2 reaches the end of the CONTROL file without having read all the data it expects Probable cause missing finish directive Action Check CONTROL file and correct CCLRC 186 Message 55 error end of CONFIG file encountered This error arises when DL_POLY_2 attempts to read more data from the CONFIG file than is actually present The probable cause is an incorrect or absent CONFIG file but it may be due to the FIELD file being incompatible in some way with the CONFIG file Action Check contents of CONFIG file If you are convinced it is correct check the FIELD file for inconsistencies Message 57 error too many core shell units specified DL_POLY_2 has a restriction of the number of types of core shell unit in the FIELD file and will terminate if too many are present Do not confuse this error with that described by message 59 below Action Standard user response Fix the parameter mxtshl Message 59 error too many core shell units in system DL_POLY_2 limits the number of core shell units in the simulated system Termination results if too many are encountered Do not confuse this error with that described by mes sage 57 above Action Standard user response Fix the parameter mxshl Message 60 error too many dihedral angles specified DL_POLY_2 will accept onl
151. k ok ok ok ok ok ok ade ade ok ok ok ok ok ale ok ok ok ok ok ale ok ok ok ok ok ale ok ok ade ade ok ale oke ok ok ale ke ok ok 2k ale C 6 1 1 2 Function PARSET is designed to provide estimates of the FORTRAN parameters e g array dimen sions required by versions of DL POLY 2 prior to 2 11 to simulate a given system i e those required for the dl params inc file By scanning the CONTROL FIELD and CONFIG files of the intended simulation PARSET is able to calculate estimates of minimum parameters needed The calculated parameters are written into a file new params inc which is FOR TRAN compatible Once this has been renamed DL PARAMS INC it can be used directly when DL POLY 2 is compiled Use of PARSET is strongly recommended as a means of reducing the effort needed to create a working DL POLY 2 executable Note PARSET is required only for versions of DL_POLY_2 prior to version 2 11 6 1 1 3 Dependencies e None PARSET is self contained 6 1 1 4 Parameters e None There are no internal arrays CCLRC 146 6 1 1 5 Input Interactive record 1 min nodes integer minimum number of processing nodes record 2 max nodes integer maximum number of processing nodes Data Files input data CONTROL Standard DL POLY 2 CONTROL input file CONFIG Standard DL POLY 2 CONFIG input file FIELD Standard DL POLY 2 FIELD input file TABLE Standard DL POLY 2 TABLE input file optional output data new params inc New parameters incl
152. l unit The core and shell carry different electric charges the sum of which equals the charge on the original atom There is no electrostatic interaction i e self interaction between the core and shell of the same atom Non Coulombic interactions arise from the shell alone The effect of an electric field is to separate the core and shell giving rise to a polarisation dipole The condition of static equilibrium gives the polarisability as a 29 qe k 2 153 where qs and qe are the shell and core charges and k is the force constant of the harmonic spring In the adiabatic method a fraction of the atomic mass is assigned to the shell to permit a dynamical description The fraction of mass is chosen to ensure that the natural frequency of vibration v of the harmonic spring i e mas 2 154 with m the atomic mass is well above the frequency of vibration of the whole atom in the bulk system Dynamically the core shell unit resembles a diatomic molecule with a harmonic bond however the high vibrational frequency of the bond prevents effective exchange of kinetic energy between the core shell unit and the remaining system Therefore from an initial condition in which the core shell units have negligible internal vibrational energy the units will remain close to this condition throughout the simulation This is essential if the core shell unit is to maintain a net polarisation In practice there is a slow leakage of kinetic energy in
153. latter The other exception is the need for 3D Fast Fourier Transform FFT routines in the Smooth Particle Mesh Ewald SPME method introduced in Version 2 12 For applications on Cray T3E D and IBM SP 2 computers the required routines are readily available in the scientific subroutine libraries routines ccfft3d and dcft3 respectively For other machines however we have assumed the public domain FF T routine fftwnd fft is available The standard Ewald sum remains available for users without access to a suitable substitute 1 3 6 Internal Data Transfer As a general policy there should be NO COMMON blocks in DL POLY 2 All nonlocal and large local arrays are passed as subroutine arguments It follows that there should be no BLOCK DATA However the introduction of the FORTRAN 90 dynamic array allocation features in DL POLY 2 version 2 11 has required the creation of a named COMMON block params to facilitate the passing of the array dimensions between subroutines Formerly the di mensions had been defined as FORTRAN parameters and incorporated in each subroutine through the include file DL PARAMS INC The COMMON block params is defined in the new version of the include file DL PARAMS INC and is included in almost all subroutines Additional COMMON blocks are also required to facilitate inter node communication via MPI and PVM 1 3 7 Internal Documentation All subroutines are supplied with a header block of FORTRAN COMMENT records
154. le or dihedral 3 A pointer array keytype Ntype itype carries the indices of the specific atoms involved in the potential term labelled type The dimension ntype will be 2 3 or 4 if the term represents a bond valence angle dihedral inversion 4 The array keytype Niype itype is used to identify the atoms in a bonded term and the appropriate form of interaction and thus to calculate the energy and forces DL_POLY_2 calculates the nonbonded pair interactions using a Verlet neighbour list 10 which is reconstructed at intervals during the simulation This list records the indices of all secondary atoms within a certain radius of each primary atom the radius being the cut off radius reut normally applied to the nonbonded potential function plus an additional increment Ar The neighbour list removes the need to scan over all atoms in the simulation at every timestep The larger radius rcu Arcyt means the same list can be used for several timesteps without requiring an update The frequency at which the list must be updated depends on the thickness of the region Arc DL POLY_2 has two methods for constructing the neighbour list the first is based on the Brode Ahlrichs scheme 22 and is used when r4 is large in comparison with the simulation cell the second uses the link cell algorithm 23 when rex is relatively small The potential energy and forces arising from the nonbonded interactions are calculated using interpola
155. lgorithm is readily implemented in the leapfrog scheme 1 1 At T EN eA x t 5 t x t 5 Unt 1 xe 5 xt 1 2 1 AtV t t At t At net AD qE AD Ee At x t 5 0 P Iu 1 WO 5 nl 1 ZA n tt A0 f t wt A E v t At At 2 l alt 70 lut 300 ule 540 N mran de Aaler Aaa AY lea AJER 2 2 2 r t 4 Zan E ir t t Ad 2 176 Like the Nos Hoover thermostat several iterations are required to obtain self consistency DL POLY 2 uses 4 iterations 5 if bond constraints are present with the standard Verlet leapfrog predictions for the initial estimates of 7 P v t and r t 3At Note also that the change in box size requires the SHAKE algorithm to be called each iteration with the new cell vectors obtained from V t4 A V exp sar nt A H t At H t exp at ne 50 2 177 where H is the cell matrix whose columns are the three cell vectors a b c CCLRC 64 The isotropic changes to cell volume are implemented in the DL_POLY routine NPT_H1 which allows for systems containing bond constraints Cell size and shape variation The isotropic algorithm may be extended to allowing the cell shape to vary by defining 7 as a tensor 7 The equations of motion are implemented as x t 340 da xt 30 A 1 TT Text x t 5 wt 580 xt 50 n t SAt nt At Ning 2 Pew u t 5 ut 550 a t 50
156. lly cited The indices 7 j and k n appearing in the pair body and three or four body terms indicate the atoms involved in the interaction There is normally a very large number of these and they are therefore specified according to atom types rather than indices In DL POLY 2 it is assumed that the pair body terms arise from van der Waals and or elec trostatic Coulombic forces The former are regarded as short ranged interactions and the latter as long ranged Long range forces require special techniques to evaluate accurately see section 2 4 In DL_POLY_2 the three body terms are restricted to valence angle and H bond forms The nonbonded three body and four body interactions are globally specified according to the types of atoms involved DL_POLY_2 also has the ability to handle metals via density dependent functions see below Though essentially many body potentials they are handled in DL_POLY_2 as special forms of pair potential In DL_POLY_2 the intramolecular bonded terms are handled using bookkeeping arrays which specify the atoms involved in a particular interaction and point to the appropriate arrays of parameters that define the potential The calculation of bonded forces therefore follows the simple scheme 1 Every atom in the simulated system is assigned a unique index number from 1 to N 2 Every intramolecular bonded term Ujype in the system has a unique index number itype from 1 to Niype where type represents a bond ang
157. lso be necessary if the Smooth Particle Mesh Ewald method is to be correctly incorporated see below Modifying the makefile Copy the makefile from the build sub directory to the source sub directory and run it there it will create the executable in the execute sub directory The compilation of the program is initiated by typing the command make target where target is the specification of the required machine e g sp2 mpi For many computer systems this command is sufficient to compile a working version of DL POLY 2 The full specification of the make command is as follows make lt TARGET gt lt STRESS gt lt TYPE gt lt EX gt lt BINROOT gt lt PVM_NODES gt where some or all of the keywords may be omitted The keywords and their use are described below Note that keywords may also be set in the unix environment e g with the setenv command in a C shell The makefile first takes each FORTRAN routine in turn and scans it with a C preprocessor The purpose of this is to activate the required features in the code and extract non selected features from the original source code For example if MPI is specified all other message passing calls pertaining to PVM for example are removed If NOSTRESS is specified the statements for calculating the stress tensor are removed The result of the preprocessing is a temporary FORTRAN file which is then compiled to produce the object code If all is
158. lue of the variable tol in QUATBOOK and recompile If problems still persist double the value of dettest in QUATBOOK and recompile If you still encounter problems contact the authors Message 320 error site in multiple rigid bodies DL_POLY_2 has detected that a site is shared by two or more rigid bodies There is no integration algorithm available in this version of the package to deal with this type of model Action The only course is to redefine the molecular model e g introducing flexible bonds and angles in suitable places to allow DL_POLY 2 to proceed Message 321 error quaternion integrator failed The quaternion algorithm has failed to converge If the maximum number of permitted iterations is exceeded the program terminates Possible causes include a bad starting configuration too large a time step used incorrect force field specification too high a tem perature inconsistent constraints involving shared atoms etc Action Corrective action depends on the cause Try reducing the timestep or running a zero kelvin CCLRC 201 structure optimization for a hundred timesteps or so It is unlikely that simply increasing the iteration number will cure the problem but you can try follow the standard user response to increase the parameter mxquat But the trouble is much more likely to be cured by careful consideration of the physical system being simulated For example is the system stressed in some way Too far from equ
159. ly simple if no angular forces are required notable exceptions to this are zeolites and silicate glasses see below Such systems require only the specification of the atomic types and the necessary pair forces The reader is referred to the description of the DL_POLY_2 FIELD file for further details section 4 1 3 DL_POLY_2 allows the simulation of zeolites and silicate or other glasses Both these materials require the use of angular forces to describe the local structure correctly In both cases the angular terms are included as three body terms the forms of which are described in chapter 2 These terms are entered into the FIELD file with the pair potentials Note that you cannot use truncated octahedral or rhombic dodecahedral boundary conditions in conjunction with three body forces due to the use of the link cell algorithm for evaluating the forces An alternative way of handling zeolites is to treat the zeolite framework as a kind of macromolecule see below This was the suggested method for users of DL_POLY_1 1 and experience showed that this is quite adequate provided it is remembered that the periodicity of the system requires that bonds be described that cross the boundaries of the MD cell and link with images of atoms from the opposite side Specifying all this is tedious and is best done computationally what is required is to determine the nearest image neighbours of all atoms and assign appropriate bond and valence angle
160. m the simulation and also controls the normal molecular dynamics cy cle which consists of forces calculation followed by integration of the equation of motion DLPOLY also monitors the cpu usage and brings about a controlled termination of the pro gram if the usage approaches the allotted job time within a pre set closure time Lastly DLPOLY is the routine that first opens the OUTPUT file section 4 2 2 which provides the summary of the job Users are recommended to study the DLPOLY root as a model for other implementations of the package they may wish to construct The dependencies and calling hierarchies of all the DL POLY 2 subroutines can be found in the Appendix of the DL POLY 2 Reference Manual If additional functionality is added to DL POLY 2 by the user the PARSET F routine and its support routines will need modifying to allow specification of the dimensions of any new arrays A description of the existing arrays found in DL POLY 2 is provided in the Appendix of the DL POLY 2 Reference Manual Any molecular dynamics simulation performs five different kinds of operation initial isation forces calculation integration of the equations of motion calculation of system properties and job termination It is worth considering these operations in turn and to in dicate which DL POLY 2 routines are available to perform them We do not give a detailed description but provide only a guide Readers are recommended to examine the different
161. machine not a hypercube The number of nodes on the parallel machine is not a power of 2 Action Specify an appropriate number of processors for job execution If you are using PVM see Action for error message 1 CCLRC 178 Message 3 error unknown directive found in CONTROL file This error most likely arises when a directive is misspelt Action Locate incorrect directive in CONTROL file and replace Message 4 error unknown directive found in FIELD file This error most likely arises when a directive is misspelt or is encountered in an incorrect lo cation in the FIELD file which can happen if too few or too many data records are included Action Locate the erroneous directive in the FIELD file and correct error Message 5 error unknown energy unit requested The DL_POLY_2 FIELD file permits a choice of units for input of energy parameters These may be electron volts ev kilocalories kcal kilojoules kj or the DL_POLY_2 internal units 10 J mol internal There is no default value Failure to specify any of these correctly or reference to other energy units will result in this error message See documen tation of the FIELD file Action Correct energy keyword on units directive in FIELD file and resubmit Message 6 error energy unit not specified A units directive is mandatory in the FIELD file This error indicates that DL_POLY_2 has failed to find the required record Action Add units directi
162. mation is requested with the ewald sum or ewald precision directives in the CONTROL file without periodic boundary conditions termination of the program results Action Select periodic boundaries by setting the variable imcon gt 0 in the CONFIG file if possible or use a different method to evaluate electrostatic interactions e g by usinf the coul directive in the CONTROL file Message 185 error too many reciprocal space vectors DL POLY 2 places hard limit on the number of k vectors to be used in the Ewald sum and terminates if more than this is requested Action Either consider using fewer k vectors in the Ewald sum and a larger cutoff in real space or follow standard user response to reset the parameters kmaxb kmaxc Message 186 error transfer buffer array too small in sysgen In the subroutine SYSGEN F DL_POLY_2 requires dimension of the array buffer defined by the parameter mxbuff to be no less than the parameter mxatms or the product of pa rameters mxnstk mxstak If this is not the case it will be unable to restart the program correctly to continue a run Applies to parallel implementations only Action Standard user response Fix the parameter mxbuff Message 190 error buffer array too small in splice DL_POLY_2 uses a workspace array named buffer in several routines Its declared size is a compromise of several r les and may sometimes be too small though in the supplied program this should happen only
163. may be used anywhere in place of the CCLRC 94 directive ewald if the user wishes to use the Smooth Particle Mesh Ewald method As a guide to beginners DL_POLY_2 will calculate reasonable parameters if the ewald precision directive is used in the CONTROL file see section 4 1 1 A relative error see below of 107 is normally sufficient so the directive ewald precision 1d 6 will cause DL POLY 2 to evaluate its best guess at the Ewald parameters a kmax1 kmax2 and kmax3 The user should note that this represents an estimate and there are some times circumstances where the estimate can be improved upon This is especially the case when the system contains a strong directional anisotropy such as a surface These four parameters may also be set explicitly by the ewald sum directive in the CONTROL file For example the directive ewald sum 0 35 6 6 8 would set a 0 35 kmaxi 6 kmax2 6 and kmax3 8 The quickest check on the accuracy of the Ewald sum is to compare the Coulombic energy U and the coulombic virial W in a short simulation Adherence to the relationship U W shows the extent to which the Ewald sum is correctly converged These variables can be found under the columns headed eng cou and vir_cou in the OUTPUT file see section 4 2 2 The remainder of this section explains the meanings of these parameters and how they can be chosen The Ewald sum can only be used in a three dimensional periodic system There
164. mber of data points specified is what DL_POLY_2 is expecting CCLRC 182 Message 25 error wrong atom type found in CONFIG file On reading the input file CONFIG DL_POLY_2 performs a check to ensure that the atoms specified in the configuration provided are compatible with the corresponding FIELD file This message results if they are not Action The possibility exists that one or both of the CONFIG or FIELD files has incorrectly specified the atoms in the system The user must locate the ambiguity using the data printed in the OUTPUT file as a guide and make the appropriate alteration Message 30 error too many chemical bonds specified DL_POLY_2 sets a limit on the number of chemical bond potentials that can be specified in the FIELD file Termination results if this number is exceeded See FIELD file docu mentation Do not confuse this error with that described by message 31 below Action Standard user response Fix parameter mxtbnd Message 31 error too many chemical bonds in system DL_POLY_2 sets a limit on the number of chemical bond potentials in the simulated system as a whole This number is a combination of the number of molecules and the number of bonds per molecule divided by the number of processing nodes Termination results if this number is exceeded Do not confuse this error with that described by message 30 above Action Standard user response Fix the parameter mxbond Message 32 error i
165. me The DL PARAMS INC file is included in all relevant subroutines at compile time 7 1 1 3 The Parameters and their Function In the following table the values of parameters that are dependent on the simulated system are given as variable Some parameter values may be derived from others and a simple formula is given An example of working parameters file can be found in the source subdirectory parameter value function CCLRC boltz kmaxb kmaxc minnode msatms msbad msgrp mslst mspmf msteth mx2tbp mx3fbp mxangl mxatms mxbond mxbuff mxcell mxcons mxdihd mxewld mxexcl mxfbd mxfld mxgatm mxgrid mxgrp mxinv mxlist mxlshp mxmols mxneut mxngp mxnstk mxpang mxpbnd mxpdih mxpfbp 0 831451115 variable variable variable gt 1 mxatms minnode 1 max mxbond mxangl mxdihd mxteth mxinv mxsh1 mxgrp minnode 1 mxatms minnode 1 variable variable variable le mxvdw variable variable variable variable max 6 mxatms 8 mxcons 1 8 mxgrp 1 mxnstk mxstak mxebuf mxgrid variable variable variable msatms or mxatms variable variable 10 variable lt mxatms variable variable variable variable 2 mxcons variable variable variable gt 3 mxsvdw 45 4 4 5 3 153 boltzmann constant in internal units max reciprocal space vector index b direction max reciprocal space vector index c direction min number of nodes for code execution max number of atoms in w
166. ments to the atomic forces not the atomic positions are passed between processors at the end of each iteration Chapter 3 DL_POLY 2 Construction and Execution CCLRC 79 Scope of Chapter This chapter describes how to compile a working version of DL POLY 2 and how to run it CCLRC 80 3 1 Constructing DL POLY 2 an Overview 3 1 1 Constructing the Standard Version DL_POLY_2 was designed as a package of useful subroutines rather than a single program which means that users were to be able to construct a working simulation program of their own design from the subroutines available which is capable of performing a specific simulation However we recognise that many perhaps most users will be content with creating a standard version that covers a wide variety if not all of the possible applications and for this reason we have provided the necessary tools to assemble such a version The method of creating the standard version is described in detail in this chapter however a brief step by step description follows 1 DL POLY 2 is supplied as a UNIX compressed tar file This must uncompressed and un tared to create the DL POLY 2 directory section 1 4 2 In the build subdirectory you will find the required DL POLY 2 makefile see section 3 2 1 and Appendix A where the main Makefile is listed This must be copied into the subdirectory containing the relevant source code In most cases this will be the source subdirectory
167. metry of molecules and as such need not have a simple relation to conventional chemical bonding DL POLY 2 makes no distinction between dihedral angle functions and improper dihedrals both are calculated by the same subroutines and all the comments made in the preceeding section apply An important example of the use of the improper dihedral is to conserve the structure of chiral centres in molecules modelled by united atom centres For example a amino acids such as alanine CH3CH NH2 COOH in which it is common to represent the CH3 and CH groups as single centres Conservation of the chirality of the o carbon is achieved by defining harmonic improper dihedral angle potential with an equilibrium angle of 35 264 The angle is defined by vectors T19 r34 and r34 where the atoms 1 2 3 and 4 are shown in the following figure The figure defines the D and L enantiomers consistent with the international IUPAC convention When defining the dihedral the atom indices are entered in DL POLY 2 in the order 1 2 3 4 L a N C 8 D a C N 8 1 2 4 1 3 The L and D enantiomers and defining vectors In DL POLY 2 improper dihedral forces are handled by the routine DIHFRC 2 2 7 Inversion Angle Potentials CCLRC 36 The inversion angle and associated vectors The inversion angle potentials describe the interaction arising from a particular ge ometry of three atoms around a central atom The best known example of this is the arrangement of hydr
168. mple analytical description e g spline potentials The force on an atom j derived from one of these potentials is formally calculated with the standard formula 1 o gn U r Tiz 2 81 f rij BS y Tjj where rj rj rj The force on atom i is the negative of this The contribution to be added to the atomic virial for each pair interaction is The contribution to be added to the atomic stress tensor is given by or ERAT 2 83 where o and 6 indicate the x y z components The atomic stress tensor derived from the pair forces is symmetric Since the calculation of pair potentials assumes a spherical cutoff Teut it is necessary to apply a long range correction to the system potential energy and virial Explicit formulae are needed for each case and are derived as follows For two atom types a and b the correction for the potential energy is calculated via the integral corr Usb on ao ju gav r Uay r r dr 2 84 V Jro where Na Np are the numbers of atoms of types a and b V is the system volume and gab r and U r are the appropriate pair correlation function and pair potential respectively It is usual to assume gay r 1 for r gt rey DL POLY_2 sometimes makes the additional assumption that the repulsive part of the short ranged potential is negligible beyond rey The correction for the system virial is Ws 3 EAA n Gs Valea 2 85 Wo das Or where the same approximations are applied Note that these formulae are
169. ms atomic velocities y component real 8 record viii only for keytrj gt 0 vzz 1 natms atomic velocities z component real 8 record ix only for keytrj gt 1 fxx 1 natms atomic forces x component real 8 record x only for keytrj gt 1 fyy 1 natms atomic forces y component real 8 record xi only for keytrj gt 1 fzz 1 natms atomic forces z component real 8 Note the implied conversion of integer variables to real on record i CCLRC 128 4 2 2 The OUTPUT File The job output consists of 7 sections Header Simulation control specifications Force field specification Summary of the initial configuration Simulation progress Summary of statistical data Sample of the final configuration and Radial distribution functions These sections are written by different subroutines at various stages of a job Creation of the OUTPUT file always results from running DL POLY 2 It is meant to be a human readable file destined for hardcopy output 4 2 2 1 Header Gives the DL_POLY_2 version number the number of processors used and a title for the job as given in the header line of the input file CONTROL This part of the file is written from the subroutines DLPOLY and SIMDEF 4 2 2 2 Simulation Control Specifications Echoes the input from the CONTROL file Some variables may be reset if illegal values were specified in the CONTROL file This part of the file is written from the subroutine SIMDEF 4 2 2 3 Force Field S
170. mula is an approximation only I I 1O UN The SHAKE algorithm calculates the constraint force Gio G that conserves the bondlength d 2 between atoms 1 and 2 following the initial movement to positions 1 and 2 under the unconstrained forces F and F3 For a system of simple diatomic molecules computation of the constraint force will in principle allow the correct atomic positions to be calculated in one pass However in the general polyatomic case this correction is merely an interim adjustment not only because the above formula is approximate but the successive correction of other bonds in a molecule has the effect of perturbing previously corrected bonds The SHAKE algorithm is therfore iterative with the correction cycle being repeated for all bonds until each has converged to the correct length within a given tolerance The tolerance may be of the order 10 Ato 1078 depending on the precision desired The procedure may be summarised as follows 1 All atoms in the system are moved using the Verlet algorithm assuming an absence of rigid bonds constraint forces This is stage 1 of the SHAKE algorithm CCLRC 59 2 The deviation in each bondlength is used to calculate the corresponding constraint force 2 160 that retrospectively corrects the bond length 3 After the correction 2 160 has been applied to all bonds every bondlength is checked If the largest deviation found exceeds the d
171. n the FIELD file follows the order in which they appear in the CONFIG file Failure to adhere to this common sequence will be detected by DL_POLY_2 and result in premature termination of the job It is therefore essential to work from the CONFIG file when constructing the FIELD file It is not as difficult as it sounds The entry of the molecular details begins with the mandatory directive molecules n where n is an integer specifying the number of different types of molecule appearing in the FIELD file Once this directive has been encountered DL_POLY_2 enters the molecular description environment in which only molecular decription keywords and data are valid Immediately following the molecules directive are the records defining individual molecules 1 name of molecule which can be any character string up to 80 characters in length Note this is not a directive just a simple character string CCLRC 113 2 nummols n where n is the number of times a molecule of this type appears in the simulated system The molecular data then follow in subsequent records 3 atoms n where n indicates the number of atoms in this type of molecule A number of records follow each giving details of the atoms in the molecule i e site names masses and charges Each record carries the entries sitnam a8 atomic site name weight real atomic site mass chge real atomic site charge nrept integer repeat counter ifrz integer frozen atom if
172. nd reset to a magnitude greater than r0 Alternatively adjust the value of r0 in the FIELD file Check that the FIELD file is correctly formatted Message 470 error n lt m in definition of n m potential The specification of a n m potential in the FIELD file implies that the exponent m is larger than exponent n Not all versions of DL_POLY_2 are affected by this Action Locate the n m potential in the FIELD file and reverse the order of the exponents Resubmit the job Message 474 error mxxdf too small in parlst subroutine The parameter mxxdf defining working arrays in subroutine PARLST of DL_POLY_2 has been found to be too small Action Standard user response Fix the parameter mxxdf CCLRC 213 Message 475 error mxxdf too small in parlst_nsq subroutine The parameter mxxdf defining working arrays in subroutine PARLST NSQ DL_POLY_2 has been found to be too small Action Standard user response Fix the parameter mxxdf Message 476 error mxxdf too small in parneulst subroutine The parameter mxxdf defining working arrays in subroutine PARNEULST is too small Action Standard user response Fix the parameter mxxdf Message 477 error mxxdf too small in prneulst subroutine The parameter mxxdf defining working arrays in subroutine PRNEULST is too small Action Standard user response Fix the parameter mxxdf Message 478 error mxxdf too small in forcesneu subroutine The parameter mxxdf defining working
173. ned by the keyword restart If this is not specified in the CONTROL file the simulation will start as new If specifed it will either continue a previous simulation restart or start a new simulation with initial temperature scaling of the previous configuration restart scale Internally these options are handled by the integer variable keyres which is explained in table 4 1 4 The various ensemble options ie nve nvt ber nvt evans nvt hoover npt ber npt hoover nst ber nst hoover are mutually exclusive though none is mandatory the default is the NVE ensemble These options are handled internally by the integer variable keyens The meaning of this variable is explained in table 4 2 5 The force selection directives ewald sum ewald precision reaction coul shift dist no elec and no vdw are handled internally by the integer variable keyfce See table 4 4 for an explanation of this variable Note that these options are mutually exclusive 6 The choice of reaction field electrostatics directive reaction requires also the spec ification of the relative dielectric constant external to the cavity This is specified in the eps directive 7 DL_POLY_2 uses as many as three different potential cutoffs These are as follows a rcut this is the universal cutoff It applies to the real space part of the elec trostatics calculations and to the van der Waals potentials if no other cutoff is applied b rvdw this is the user
174. not confuse this with message 303 above Action Standard user response Fix the parameter mxgatms Message 305 error box size too small for link cells The link cells algorithm in DL_POLY_2 cannot work with less than 27 link cells Depending on the cell size and the chosen cut off DL_POLY_2 may decide that this minimum cannot be achieved and terminate CCLRC 200 Action If a smaller cut off is acceptable use it Otherwise do not use link cells Consider running a larger system where link cells will work Message 306 error failed to find principal axis system This error indicates that the routine QUATBOOK has failed to find the principal axis for a rigid unit Action This is an unlikely error The code should correctly handle linear planar and 3 dimensional rigid units Check the definition of the rigid unit in the CONFIG file if sensible report the error to the authors Message 310 error quaternion setup failed This error indicates that the routine QUATBOOK has failed to reproduce all the atomic po sitions in rigid units from the centre of mass and quaternion vectors it has calculated Action Check the contents of the CONFIG file DL_POLY_2 builds its local body description of a rigid unit type from the first occurrence of such a unit in the CONFIG file The error most likely occurs because subsequent occurrences were not sufficiently similar to this reference structure If the problem persists increase the va
175. nteger array memory allocation failure DL_POLY_2 has failed to allocate sufficient memory to accommodate one or more of the integer arrays in the code Action This may simply mean that your simulation is too large for the machine you are running on Consider this before wasting time trying a fix Try using more processing nodes if they are available If this is not an option investigate the possibility of increasing the heap size for your application Talk to your systems support people for advice on how to do this Message 33 error real array memory allocation failure DL_POLY_2 has failed to allocate sufficient memory to accommodate one or more of the real arrays in the code CCLRC 183 Action This may simply mean that your simulation is too large for the machine you are running on Consider this before wasting time trying a fix Try using more processing nodes if they are available If this is not an option investigate the possibility of increasing the heap size for your application Talk to your systems support people for advice on how to do this Message 34 error character array memory allocation failure DL_POLY_2 has failed to allocate sufficient memory to accommodate one or more of the character arrays in the code Action This may simply mean that your simulation is too large for the machine you are running on Consider this before wasting time trying a fix Try using more processing nodes if they are available If t
176. ntegration Only one iteration is needed two if the system has bond constraints to constrain the instantaneous temperature to exactly Text however energy is not conserved by this algorithm The algorithm is implemented in the DL_POLY routines NVT_EO and NVT El The latter is for systems with bond constraints 2 5 5 Barostats The size and shape of the simulation cell may be dynamically adjusted by coupling the system to a barostat in order to obtain a desired average pressure Pext and or isotropic stress tensor c DL POLY 2 has two such algorithms a Hoover type barostat and the Berendsen barostat Only the former has a well defined conserved quantity 2 5 5 1 The Hoover Barostat DL_POLY_2 uses the Melchionna modification of the Hoover algorithm 37 in which the equations of motion involve a Nos Hoover thermostat and a barostat in the same spirit Cell size variation For isotropic fluctuations the equations of motion are dr t v t n r t Ro dt du qa x t n t v t CCLRC 63 dx t 1 1 T2 Text dn t 1 ae Mura OP et YO prova 2174 where 7 is the barostat friction coefficient Ro the system centre of mass Tp a specified time constant for pressure fluctuations P the instantaneous pressure and V the system volume The conserved quantity is to within a constant the Gibbs free energy of the system 3N kp Text a n t 72 2 175 Jiu Pr HynvrT PextV t The a
177. ntials The valence angle and associated vectors The valence angle potentials describe the bond bending terms between the specified atoms They should not be confused with the three body potentials described later which are defined by atom types rather than indices 1 Harmonic harm k U 65i 5 Ojik 9 2 12 2 Quartic quar k 2 k 3 k i U Ojik 5 Ojik 00 z Ojik 00 Ojik 00 2 13 2 3 4 CCLRC 3 Truncated harmonic thrm k U Ojik 2 Ojik 00 exp rj rik 0 4 Screened harmonic shrm U Ojik E Orin 0o exp rij P1 rix p2 5 Screened Vessal 24 bvs1 k 2 212 som lo jin 7 j exp rij p1 rix 2 U Ojik 6 Truncated Vessal 25 bvs2 a a U Ojik k 5i Bj 90 Ojir 00 27 ud gt Ojik 00 rr 69 expl r 4 107 7 Harmonic cosine hcos U Ojik gt c0 0ju cos 00 8 Cosine cos U Ojik A L cos mOjix 6 In these formulae 05 is the angle between bond vectors rj and rig 1 Lij Lik Ojik cos 12 IL Tijfik 30 2 14 2 15 2 16 2 17 2 18 2 19 2 20 In DL_POLY_2 the most general form for the valence angle potentials can be written as U Ojik Tijs Tik AlO jik S rij S rix 2 21 where A 0 is a purely angular function and S r is a screening or truncation function All the
178. nts are converged 8 After convergence the coordinate arrays on each node are passed to all the other nodes The coordinates of atoms that are not in the constraint list of a given node are taken from the incoming arrays an operation we term splicing 9 Finally the change in the atom positions is used to calculate the atomic velocities This scheme contains a number of non trivial operations which are described in detail in 30 However some general comments are worth making The compilation of the list of constrained atoms on each node and the circulation of the list items 1 3 above need only be done once in any given simulation It also transpires that in sharing bond contraints between nodes there is an advantage to keeping as many of the constraints pertaining to a particular molecule together on one node as is possible within the requirement for load balancing This reduces the data that need to be transferred between nodes during the iteration cycle It is also advantageous if the molecules are small to adjust the load balancing between processors to prevent shared atoms The loss of balance is compensated by the elimination of communications during the SHAKE cycle These techniques are exploited by DL POLY 2 CCLRC 77 The QSHAKE algorithm is an extension of the SHAKE algorithm for constraint bonds between rigid bodies The parallel strategy is very similar to that of RD SHAKE The only significant difference is that incre
179. o small relative r m s fluctuations in the total energy of 10 are typical with this algorithm The algorithm requires values of position r and force f at time t while the velocities v are half a timestep behind The first step is to advance the velocities to t 1 2 At by integration of the force uid sat age an At o 2 155 where m is the mass of a site and At is the timestep The positions are then advanced using the new velocities r t At r t At v t sat 2 156 Molecular dynamics simulations normally require properties that depend on position and velocity at the same time such as the sum of potential and kinetic energy The velocity at time t is obtained from the average of the velocities half a timestep either side of time t i i i v t a v t 344 T v t At 2 157 The instantaneous temperature for example can then be obtained from the atomic velocities assuming the system has no net momentum E mun mv t a kgf where i labels particles which can be atoms or rigid molecules A the number of particles in the system kg Boltzmanns constant and f the number of degrees of freedom in the system 3M 3 if the system is periodic and without constraints The routine NVE_0 implements the Verlet leapfrog algorithm and calculates the instan taneous temperature The conserved quantity is the total energy of the system T 2 158 Hnve U KE 2 159 where U is the potential energy of the s
180. of rigid bodies the atomic forces are resolved into molecular forces and torques These matters are discussed in greater detail later in sections 2 5 1 and 2 5 6 Note that the subroutines mentioned in the subsections of this chapter are described in greater detail in chapter 7 2 2 The Intramolecular Potential Functions In this section we catalogue and describe the forms of potential function available in DL_POLY_2 The key words required to select potential forms are given in brackets before each definition The derivations of the atomic forces virial and stress tensor are also outlined 2 2 1 Bond Potentials laz 1 The interatomic bond vector The bond potentials describe explicit bonds between specified atoms They are functions of the interatomic distance only The potential functions available are as follows 1 Harmonic bond harm Vine jr ny 2 2 CCLRC 28 2 Morse potential mors U rij EoH1 exp k rij ro 1 2 3 3 12 6 potential bond 12 6 4 Restrained harmonic rhrm 1 Org ro lrig T0 re 2 5 1 U r PLU t kre rij Tol rc rij ro 2 6 5 Quartic potential quar k 2 k 3 k i U rij 3 r To zly To gu To 2 7 In these formulae r is the distance between atoms labelled and j Tjj Ir m 2 8 where ry is the position vector of an atom labelled The force on the atom j arising from a bond potenti
181. off are therefore much less severe than if an atomistic scheme is used In DL_POLY_2 the interaction is evaluated between all atoms of both groups if any site of the first group is within the cutoff distance of any site of the second group The groups are known interchangeably as charge groups or neutral groups in the documentation which serves as a reminder that the advantages of using such a scheme are lost if the groups carry an overall charge There is no formal requirement in DL POLY 2 that the groups actually be electrically neutral The charge group scheme is more cpu intensive than a simple atomistic cutoff scheme as more computation is required to determine whether or not to include a set of interactions However the size of the Verlet neighbourhood list easily the largest array in DL POLY 2 is considerably smaller with a charge group scheme than an atomistic scheme as only a list of interacting groups need be stored as opposed to a list of interacting atoms 2 4 2 Direct Coulomb Sum Use of the direct Coulomb sum is sometimes necessary for accurate simulation of isolated nonperiodic systems It is not recommended for periodic systems The interaction potential for two charged ions is l diqj 47 0 Tij U rij 2 112 with ge the charge on an atom labelled and r the magnitude of the separation vector Tjj Tj Tj The force on an atom j derived from this force is l 99 s T 2 113 j Arme ri Tij
182. ogen atoms around nitrogen in ammonia to form a trigonal pyramid The hydrogens can flip like an inverting umbrella to an alternative structure which in this case is identical but in principle causes a change in chirality The force restraining the ammonia to one structure can be described as an inversion potential though it is usually augmented by valence angle potentials also The inversion angle is defined in the figure above note that the inversion angle potential is a sum of the three possible in version angle terms It resembles a dihedral potential in that it requires the specification of four atomic positions The potential functions available in DL_POLY_2 are as follows 1 Harmonic harm U ijkn a isin bo 2 51 2 Harmonic cosine hcos U ditkn cos diam cos do 2 52 3 Planar potential plan U dijkn A 1 cos dijkn 2 53 In these formulae 4n is the inversion angle defined by To da E 2 54 TijWkn with Wyn Lij pn pn Lij Pas Oa 2 55 and the unit vectors p fik fin fie faul Fik En la Bak 2 56 Ukn CCLRC 37 As usual Tij Ly Ly ete and the hat f indicates a unit vector in the direction of r The total inversion potential requires the calculation of three such angles the formula being derived from the above using the cyclic permutation of the indices j gt k gt n j etc Equivalently the angle jj may be written a
183. ogy Users wishing to add new features DL_POLY_2 will need to be familiar with the underlying techniques as they are described in greater detail in references 30 42 2 6 1 The Replicated Data Strategy The Replicated Data RD strategy 41 is one of several ways to achieve parallelisation in MD Its name derives from the replication of the configuration data on each node of a parallel computer i e the arrays defining the atomic coordinates r velocities v and forces f for all N atoms i i 1 N in the simulated system are reproduced on every processing node In this strategy most of the forces computation and integration of the equations of motion can be shared easily and equally between nodes and to a large extent be processed independently on each node T he method is relatively simple to program and is reasonably efficient Moreover it can be collapsed to run on a single processor very easily However the strategy can be expensive in memory and have high communication overheads but overall it has proven to be successful over a wide range of applications These issues are explored in more detail in 41 42 Systems containing complex molecules present several difficulties They often contain ionic species which usually require Ewald summation methods 10 43 and intra molecular interactions in addition to inter molecular forces These are handled easily in the RD strategy though the SHAKE algorithm 11 requires signif
184. ontinues but even in this case DL_POLY_2 will terminate the job at a more appropriate place This feature is used in processing the CONTROL and FIELD file directives A possible modification users may consider is to dump additional data before the call to ERROR is made A description of the ERROR subroutine is found in chapter 7 the DL POLY 2 Reference Manual A full list of the DL_POLY_2 error messages and the appropriate user action can be found in Appendix C of this document Chapter 4 DL_POLY_2 Data Files CCLRC 98 Scope of Chapter This chapter describes all the input and output files for DL_POLY_2 examples of which are to be found in the data sub directory CCLRC 99 4 1 The INPUT files E Q e E Figure 4 1 DL POLY 2 input left and output right files Note files marked with an asterisk are non mandatory DL POLY 2 requires five input files named CONTROL CONFIG FIELD TABLE and REVOLD The first three files are mandatory while TABLE is used only to input certain kinds of pair potential and is not always required REVOLD is required only if the job represents a continuation of a previous job In the following sections we describe the form and content of these files 4 1 1 The CONTROL File The CONTROL file is read by the subroutine SIMDEF and defines the control variables for running a DL POLY 2 job It makes extensive use of directives and key words Directives are character strings that appear as th
185. ontrolled by the first order differential equation dx t _ 1 _ 1 2 165 dt T2 Text where rr is a specified time constant normally in the range 0 5 2 ps In DL POLY 2 x is stored at half timesteps as it has dimensions of 1 time The integration takes place as 1 1 At T XE zan xlt za0 75 d 1 xt 5 xtt 580 xt 340 2 f t wet A ot At at 20 xO of 5 lut AD u t A0 HELAD Elo 4 DEES sat 2 166 Since v t is required to calculate T and itself the algorithm requires several iterations to obtain self consistency In DL_POLY_2 the number of iterations is set to 3 4 if the system has bond constraints The iteration procedure is started with the standard Verlet leapfrog prediction of v t and 7 The conserved quantity is derived from the extended Hamiltonian CCLRC 61 for the system which to within a constant is the Helmholtz free energy TAX t Huvt Hyve fkeText Eon f xus 2 167 o If bond constraints are present an extra iteration is required due to the call to the SHAKE routine Note that the SHAKE corrections need only be applied during the first iteration as subsequent to this the velocities relative to the bond c o m velocity will be orthogonal to the bond vectors The velocity scaling imposed by the thermostat is isotropic so does not destroy this orthogonality The algorithm is implemented in the DL POLY routines NVT H and NVT Hl the latter being for system
186. orking arrays max size of working arrays for bond angle dihedral tether inversion and shell routines max number of rigid groups per node max number of atoms in Verlet test arrays max number of potential of mean force constraints per node max number of tethered atoms per node array dimension of 3 body potential parameters array dimension of 4 body potential parameters max number of bond angles on a node max number of atoms in system max number of chemical bonds on a node max dimension of atomic transfer buffer max number of link cells in system max number of constraint bonds on a node max number of torsion angles on a node max of array elements in EWALD1 A work arrays max number of excluded interactions per atom max number of defined 4 body force potentials max number of external field parameters max number of sites in rigid units max number of grid points in potential arrays max number of rigid body units in system max number of inversion potentials per node max number of atoms in verlet list max dimension of shape routine transfer array max number of molecules max number of neutral groups 1 max number of sites in a rigid unit max number of stacked variables max number of angle potential parameters max number of bond potential parameters max number of dihedral potential parameters max number of 4 body potential parameters CCLRC mxpinv mxpmf mxproc mxptbp mxpvdw mxquat mxrdf mxshak mxshl mxsi
187. otential keyword appears in columns 17 20 of the FIELD file Message 153 error metals not permitted with multiple timestep The multiple timestep algorithm cannot be used in conjunction with metal potentials in DL_POLY 2 Action The simulation must be run without the multiple timestep option Message 160 error unaccounted for atoms in exclude list This error message means that DL_POLY_2 has been unable to find all the atoms described in the exclusion list within the simulation cell This should never occur if it does it means a serious bookkeeping error has occured The probable cause is corruption of the code somehow Action If you feel you can tackle it good luck Otherwise we recommend you get in touch with the program authors Keep all relevant data files to help them find the problem Message 170 error too many variables for statistic array This error means the statistics arrays appearing in subroutine STATIC are too small This can happen if the number of unique atom types is too large CCLRC 197 Action Standard user response Fix the parameter mxnstk mxnstk should be at least 45 number of unique atom types Message 180 error Ewald sum requested in non periodic system DL_POLY_2 can use either the Ewald method or direct summation to calculate the elec trostatic potentials and forces in periodic or pseudo periodic systems For non periodic systems only direct summation is possible If the Ewald sum
188. pecification Echoes the FIELD file A warning line will be printed if the system is not electrically neutral This warning will appear immediately before the non bonded short range potential specifications This part of the file is written from the subroutine SYSDEF 4 2 2 4 Summary of the Initial Configuration This part of the file is written from the subroutine SYSGEN It states the periodic boundary specification the cell vectors and volume if appropriate and the initial configuration of a maximum of 20 atoms in the system The configuration information given is based on the value of levcfg in the CONFIG file If levcfg is 0 or 1 positions and velocities of the 20 atoms are listed If levcfg is 2 forces are also written out For periodic systems this is followed by the long range corrections to the energy and pressure 4 2 2 5 Simulation Progress This part of the file is written by the DL POLY 2 root segment DLPOLY The header line is printed at the top of each page as step eng tot temp tot eng cfg eng vdw eng cou eng bnd eng ang eng dih eng tet time ps eng pv temp rot vir cfg vir vdw vir cou vir bnd vir ang vir con vir tet cpu s volume temp shl eng shl vir shl alpha beta gamma vir pmf press CCLRC 129 The labels refer to line 1 step eng tot temp_tot eng cfg eng vdw eng cou eng bnd eng ang eng dih eng tet line 2 time ps eng pv temp rot vir cfg vir vdw vir cou vir bnd vir ang vir_con vir_
189. piled to over all the likely uses of the code It is not foolproof however Sometimes an estimate of the required array sizes is difficult to obtain and the calculated value may be too small For this reason DL POLY 2 retains all the old array dimension checks and will terminate as before when an array bound error occurs When a dimension error occurs the standard user response is to edit the DL POLY 2 subroutine PARSET F Locate where the variable defining the array dimension is fixed and increase accordingly To do this you should make use of the dimension information that DL POLY 2 prints in the OUTPUT file prior to termination If no information is supplied simply doubling the size of the variable will usually do the trick If the variable concerned is defined in one of the support subroutines CFGSCAN F FLDSCAN F CONSCAN F you will need to insert a new line in PARSET F to redefine it after the relevant subroutine has been called Finally the code must be recompiled but in this case it will be necessary only to recompile PARSET F and not the whole code The DL POLY 2 Error Messages Message 1 error PVM NODES unset The code was C preprocessed with the flag DPVM set but the number of PVM nodes was not stated Action Delete the module INITCOMMS o from the source directory and re make the executable this time including the directive PVM NODES n where n is the number of nodes you require with the make command Message 2 error
190. potentials This may require the definition of new bond forces in subroutine BNDFRC but this is easy What must be avoided at all costs is specifying the angle potentials without specifying bond potentials In this case DL_POLY_2 will automatically cancel the non bonded forces between atoms linked via valence angles and the system will collapse The advantage of this method is that the calculation is likely to be faster using three body forces This method is not recommended for amorphous systems 3 3 2 Macromolecules Simulations of proteins are best tackled using the package DLPROTEIN 21 which is an adaptation of DL POLY specific to protein modelling However you may simulate proteins and other macromolecules with DL POLY 2 if you wish This is described below If you select a protein structure from a SEQNET file e g from the Brookhaven database use the utility PROSEQ to generate the file CONFIG This will then function as input for DL POLY 2 Some caution is required here however as the protein structure may not be fully determined and atoms may be missing from the CONFIG file If you have the edit out file produced by AMBER for your molecule use this as the CONNECT DAT input file for the utility AMBFORCE AMBFORCE will produce the DL POLY 2 FIELD and CONFIG files for your molecule If you do not have the edit out file things are a little more tricky particularly in CCLRC 93 coming up with appropriate partial charge
191. qarch pwr2 qtune pwr2 TIMER OBJ_SPME CPFLAGS D STRESS DSERIAL D POINTER integer EX EX BINROOT BINROOT TYPE R8 6000 Power3 serial rs6k pwr3 dpp MAKE LD x1f o LDFLAGS L usr local lib lmass lessl FC xlf FFLAGS c 0 qnosave qarch pwr3 TIMER A CPFLAGS D STRESS DSERIAL DESSL D POINTER integer OCCLRC 165 EX EX BINROOT BINROOT TYPE pentium absoft dpp MAKE LD usr bin f90 o LDFLAGS lfio TIMER QBJ SPME VN FC usr bin f90 FFLAGS c YEXT NAMES LCS B108 B100 0 CPFLAGS D STRESS DSERIAL P D POINTER integer V EX EX BINROOT BINROOT TYPE PentiumII portland serial no SPME pentium portland dpp MAKE LD usr local pgi linux86 bin pgf90 o LDFLAGS N FC usr local pgi linux86 bin pgf90 FFLAGS c 0 Mdalign CPFLAGS D STRESS DSERIAL P D POINTER integer TIMER OBJ_SPME EX EX BINROOT BINROOT TYPE Hitachi SR2201 Multiprocessor no SPME hitachi sr2201 dpp cp usr include mpif h mpif h MAKE FC xf90 FFLAGS c WO form fixed opt o 3 langlvl save 0 s TRACE CPFLAGS D STRESS DMPI D POINTER integer intlist o MAKE LDFLAGS LDLIBS 1fmpi lmpi LD xf90 o FC xf90 FFLAGS c WO form fixed opt 0 3 langlvl save 0 s TR
192. quired is the FIELD file section 4 1 3 which specifies the nature of the intermolecular interactions the molecular topology and the atomic properties such as charge and mass Sometimes you will require a fourth file TABLE section 4 1 5 which contains the potential and force arrays for functional forms not available within DL POLY 2 usually because they are too complex e g spline potentials Examples of input files are found in the data sub directory which can be copied into the execute subdirectory using the select macro found in the execute sub directory A successful run of DL POLY 2 will generate several data files which appear in the execute sub directory The most obvious one is the file OUTPUT section 4 2 2 which provides an effective summary of the job run the input information starting configura tion instantaneous and rolling averaged thermodynamic data final configurations radial distribution functions RDFs and job timing data The OUTPUT file is human readable Also present will be the restart files REVIVE section 4 2 4 and REVCON section 4 2 3 REVIVE contains the accumulated data for a number of thermodynamic quantities and RDFs and is intended to be used as the input file for a following run It is not human readable The REVCON file contains the restart configuration i e the final positions ve locities and forces of the atoms when the run ended and is human readable The STATIS file section 4 2 7 contains
193. r This directive and associated data records need not be specified if the molecule contains no rigid units See the note on the atomic indices appearing under the shell directive above teth n where n is the number of tethered atoms in the molecule It is followed by n records specifying the tethered sites in the molecule CCLRC 119 13 tether key ad tethering potential key see table 4 11 index integer atomic index variable 1 real potential parameter see table 4 11 variable 2 real potential parameter see table 4 11 variable 3 real potential parameter see table 4 11 variable 4 real potential parameter see table 4 11 This directive and associated data records need not be specified if the molecule contains no tethered atoms See the note on the atomic indices appearing under the shell directive above Table 4 11 Tethering potentials potential type Variables 1 3 functional form harm Harmonic k rhrm Restraint k re U r kr T X Te U ikr2 kre r re T Te Quartic k k k U r Er Epi Epi finish This directive is entered to signal to DL_POLY_2 that the entry of the details of a molecule has been completed The entries for a second molecule may now be entered beginning with the name of molecule record and ending with the finish directive The cycle is repeated until all the types of molecules indicated by the molecules directive have been entered The user is recommended to look at th
194. r too many four body potentials specified Too many four body potential have been defined in the FIELD file Certain arrays must be increased in size to accommodate the data Action Standard user response Fix the parameter mxfbp Message 90 error system total electric charge nonzero In DL POLY 2 a check on the total system charge will result in an error if the net charge of the system is nonzero Note In DL POLY 2 this message has been disabled The program merely prints warning stating that the system is not electrically neutral but it does not CCLRC 191 terminate the program watch out for this Action Check the specified atomic charges and their populations Make sure they add up to zero If the system is required to have a net zero charge you can enable the call to this error message in subroutine SYSDEF Message 91 error unidentified atom in 4 body potential list The specification of a four body potential in the FIELD file has referenced an atom type that is unknown Action Locate the errant atom type in the four body potential definition in the FIELD file and correct Make sure this atom type is specified by an atoms directive earlier in the file Message 93 error cannot use shell model with rigid molecules The dynamical shell model implemented in DL_POLY_2 is not designed to work with rigid molecules This error results if these two options are simultaneously selected Action In some circum
195. r It is invoked by the routine CSEND Action Check your system implementation of PVM Message 500 error in crecv pvmfrecv The PVM routine PVMFRECV has returned an error It is invoked by the routine CRECV Action Check your system implementation of PVM Message 502 error in crecv pvmfunpack The PVM routine PVMFUNPACK has returned an error It is invoked by the routine CRECV CCLRC 215 Action Check your system implementation of PVM Message 504 error cutoff too large for TABLE file The requested cutoff exceeds the information in the TABLE file Action Reduce the value of the vdw cutoff rvdw in the CONTROL file or reconstruct the TABLE file Message 506 error work arrays too small for quaternion integration The working arrays associated with quaternions are too small for the size of system being simulated They must be redimensioned Action Standard user response Fix the parameter msgrp Message 508 error rigid bodies not permitted with RESPA algorithm The RESPA algorithm implemented in DL_POLY_2 is for atomic systems only Rigid bod ies or constraints cannot be treated Action There is no cure for this The code simply does not have this capability Consider writing it for yourself Message 510 error structure optimiser not permitted with RESPA The RESPA algorithm in DL_POLY_2 has not been implemented to work with the struc ture optimizer You have asked for a forbidden operation
196. r fc found in the real space sum should be noted The total electrostatic energy is given by the following formula B Te amp exp a exp k 4a a djdn Uu x eC EDDY a explil nj f Y er fears kz0 n lt j 1 I Sie a 5 Y Uam in 15 gt 2 129 treo molecules lt m vm Tom ve where N is the number of ions in the system and N the same number discounting any excluded intramolecular interactions M represents the number of excluded atoms in a given molecule and includes the atomic self correction V is the simulation cell volume and k is a reciprocal lattice vector defined by k u mv nw 2 130 3Strictly speaking the real space sum ranges over all periodic images of the simulation cell but in the DL_POLY_2 implementation the parameters are chosen to restrict the sum to the simulation cell and its nearest neighbours i e the minimum images of the cell contents CCLRC 51 where m n are integers and u v w are the reciprocal space basis vectors Both V and u v w are derived from the vectors a b c defining the simulation cell Thus Vo la b x cl 2 131 and bxc 2 A T a bxc cxa 2 2 132 x a bxc w 2r axb a bxc With these definitions the Ewald formula above is applicable to general periodic systems A small additional modification is necessary for rhombic dodecahedral and truncated oc tahedral simulation cells 30 In practice the convergence of the Ewald sum is controlle
197. rds mzrdf records radius real e14 interatomic distance A g r real e14 RDF at given radius Note the RDFDAT file is optional and appears when the print rdf option is specified in the CONTROL file 4 2 6 The ZDNDAT File This is a formatted file containing the Z density data Its contents are as follows record 1 cfgname character A80 configuration name record 2 mxrdf integer 110 number of data points in the Z density function following records mzrdf records Zz real e14 distance in z direction A p z real e14 Z density at given height z Note the ZDNDAT file is optional and appears when the print rdf option is specified in the CONTROL file 4 2 7 The STATIS File The file is formatted with integers as i10 and reals as el4 6 It is written by the subroutine STATIC It consists of two header records followed by many data records of statistical data record 1 cfgname character configuration name record 2 string character energy units CCLRC 133 Data records Subsequent lines contain the instantaneous values of statistical variables dumped from the array stpval A specified number of entries of stpval are written in the format 1p 5e14 6 The number of array elements required determined by the parameter mxnstk in the DL_PARAMS INC file is mxnstk gt 27 ntpatm number of unique atomic sites 9 if stress tensor calculated 9 if constant pressure simulation requested The STA
198. re mean squared displacement of first atom types mean squared displacement of second atom types mean squared displacement of last atom types the next 9 entries if the stress tensor is calculated xx component of stress tensor xy component of stress tensor xz component of stress tensor yx component of stress tensor zz component of stress tensor the next 9 entries if a NPT simulation is undertaken engshl real virshl real alpha real beta real gamma real record vii stpval 26 stpval 27 virpmf real press real the next ntpatm entries amsd 1 real amsd 2 real amsd ntpatm real stress 1 real stress 2 real stress 3 real stress 4 real zu real stress 9 real cell 1 real cel11 2 real cell 3 real cell 4 real Lu real cell 9 real x component of a cell vector y component of a cell vector z component of a cell vector x component of b cell vector z component of c cell vector Note The stress tensor is calculated only if the code is compiled with the STRESS option see section 3 2 1 Cell shape varying constant pressure simulations keyword en semble nst in the CONTROL file are only possible if the stress tensor is calculated If isotropic constant pressure simulations are required where the cell volume but not the shape may vary keyword ensemble npt the stress tensor need not be calculated CCLRC 135 Table 4 12 Definition of pair potential functions and variables potential type Var
199. re m distinct types of atom in the system the index can possibly range from 1 to m m 1 m 2 6 If the internally calculated index exceeds this number this error report results Action Standard user response Fix the parameter mxfbp Message 102 error parameter mxproc exceeded in shake arrays The RD SHAKE algorithm distributes data over all nodes of a parallel computer Certain arrays in RD SHAKE have a minimum dimension equal to the maximum number of nodes DL_POLY_2 is likely to encounter If the actual number of nodes exceeds this the program CCLRC 193 terminates Action Standard user response Fix the parameter mxproc Message 103 error parameter mxlshp exceeded in shake arrays The RD SHAKE algorithm requires that information about shared atoms be passed be tween nodes If there are too many atoms the arrays holding the information will be exceeded and DL_POLY_2 will terminate execution Action Standard user response Fix the parameter mxlshp Message 105 error shake algorithm failed to converge The RD SHAKE algorithm for bond constraints is iterative If the maximum number of permitted iterations is exceeded the program terminates Possible causes include a bad starting configuration too large a time step used incorrect force field specification too high a temperature inconsistent constraints involving shared atoms etc Action Corrective action depends on the cause It is unlikely
200. reated as a rigid body 5 1 1 5 Test Case 5 Shell model of MgCl at constant pressure Dynamical Shell model simulation of MgClo Temperature and pressure are controlled by a Berendsen thermostat and barostat An Ewald sum is used with cubic periodic boundary conditions 5 1 1 6 Test Case 6 PMF calculation Potential of mean force calculation of a potassium ion in SPC water Electrostatics are handled by the Ewald sum The water is treated as a constrained triangle 5 1 1 7 Test Case 7 Linked rigid bodies at constant pressure 8 biphenyl molecules in cubic boundary conditions Temperature and pressure are con trolled by a Hoover type thermostat and barostat Each phenyl ring is treated as a rigid body with a constraint bond to the other ring of the molecule In the centre of each ring are three massless charge sites which imparts a quadrupole moment to the ring 5 1 1 8 Test Case 8 An osmosis experiment with a semi permeable membrane The membrane is a collection of tethered sites interconnected by harmonic springs There are no electrostatic forces in the system The simulation is run with the Hoover anisotropic constant presure algorithm 5 1 1 9 Test Case 9 A surfactant at the air water interface The system is comprised of 32 surfactant molecules trimethylaminododecane bromide or TAB C12 arranged either side of a slab of 342 water molecules approximately 30 Athick The surfactant chains are treated with rigid bonds and the water
201. red from the source sub directory at compile time It is not necessary for the user to copy them over 1 4 9 The sdk Sub directory The DL POLY_2 Graphical User Interface GUI is based on the CERIUS Visualiser from Molecular Simulations Inc The subroutines written by Daresbury Laboratory are to be found in this sub directory However alone they are insufficient to create a working GUI but DL POLY 2 users who have access to MSI s SDK Software Development Kit will be able to use these subroutines as a starting place for constructing and modifying the DL_POLY_2 GUI For DL POLY_2 users without this resource a compiled version of the GUI is available for Silicon Graphics computers running the CERIUS Visualiser version 3 5 See the document The DL POLY 2 Graphical User Interface by W Smith 20 CCLRC 21 1 5 Obtaining the Source Code To obtain a copy of DL_POLY_2 it is first necessary to obtain a licence from Daresbury Laboratory A copy of the licence form may be obtained in two ways either by selecting the licence button on the World Wide Web page http www dl ac uk TCSC Software DL POLY main html and downloading and printing the file or by using FTP to copy the postscript file from the CCP5 Program Library at Daresbury Laboratory in the following manner 1 move to the desired directory on YOUR machine 2 type ftp ftp dl ac uk 3 enter userid anonymous 4 enter passwd use your name and site 5 change
202. ribute to the ezcluded atoms list see section 2 1 In this case DL POLY 2 will calculate the nonbonded pair potentials between the described atoms CCLRC 117 9 dihedrals n where n is the number of dihedral interactions present in the molecule Each of the following n records contains dihedral key ad potential key See table 4 9 index 1 integer first atomic index index 2 integer second atomic index index 3 integer third atomic index index 4 integer fourth atomic index variable 1 real potential parameter see table 4 9 variable 2 real potential parameter see table 4 9 variable 3 real potential parameter see table 4 9 variable 4 real 1 4 electrostatic interaction scale factor variable 5 real 1 4 Van der Waals interaction scale factor The meaning of the variables 1 3 is given in table 4 9 The variables 4 and 5 specify the scaling factor for the 1 4 electrostatic and Van der Waals nonbonded interactions respectively This directive and associated data records need not be specified if the molecule contains no dihedral angle terms See the note on the atomic indices appearing under the shell directive above Table 4 9 Dihedral Angle Potentials potential type Variables 1 3 functional formt Cosine U A 1 cos m Harmonic sk do Harmonic cosine U cos cos o Triple cosine U 5A1 1 cos 542 1 cos 2 543 1 cos 3 1 is the a b c d dihedral angle
203. rnational Vessal B 1994 J Non Cryst Solids 177 103 Smith W Greaves G N and Gillan M J 1995 J Chem Phys 103 3091 Smith W 1993 CCP3 Information Quarterly 39 14 Clarke J H R Smith W and Woodcock L V 1986 J Chem Phys 84 2290 Finnis M W and Sinclair J E 1984 Philos Mag A 50 45 Eastwood J W Hockney R W and Lawrence D N 1980 Comput Phys Com mun 19 215 Smith W and Fincham D 1993 Molecular Simulation 10 67 Essmann U Perera L Berkowitz M L Darden T Lee H and Pedersen L G 1995 J Chem Phys 103 8577 Neumann M 1985 J Chem Phys 82 5663 Fincham D and Mitchell P J 1993 J Phys Condens Matter 5 1031 Lindan P J D and Gillan M J 1993 J Phys Condens Matter 5 1019 McCammon J A and Harvey S C 1987 Dynamics of Proteins and Nucleic Acids Cambridge University Press Brown D and Clarke J H R 1984 Molec Phys 51 1243 Melchionna S Ciccotti G and Holian B L 1993 Molec Phys 78 533 Tildesley D J Streett W B and Saville G 1978 Molec Phys 35 639 Tildesley D J and Streett W B Multiple time step methods and an improved potential function for molecular dynamics simulations of molecular liquids In Lykos P editor Computer Modelling of Matter ACS Symposium Series No 86 1978 40 Forester T and Smith W 1994 Molecular Simulation 13 195
204. rode Ahlrichs approach This makes the Verlet list considerably smaller thus saving memory but also results in a more coarse grain parallelism The consequence of which is that performance CCLRC 75 with a large number of processors will degrade more quickly than with the atomistic scheme Once the neighbour list has been constructed each node of the parallel computer may proceed independently to calculate the pair force contributions to the atomic forces 2 6 4 Modifications for the Ewald Sum For systems with periodic boundary conditions DL_POLY_2 employs the Ewald Sum to calculate the Coulombic interactions see section 2 4 5 Calculation of the real space component in DL_POLY_2 employs the algorithm for the calculation of the nonbonded interactions outlined above The reciprocal space component is calculated using the schemes described in 43 in which the calculation can be paral lelised by distribution of either k vectors or atomic sites Distribution over atomic sites requires the use of a global summation of the q exp ik terms but is more efficient in memory usage Both strategies are computationally straightforward Subroutine EWALD1 distributes over atomic sites and is often the more efficient of the two approaches Subrou tine EWALD1A distributes over the k vectors and may be more efficient on machines with large communication latencies Other routines required to calculate the ewald sum include EWALD2 EWALD3 and
205. rticular three body potential in the following manner atmnam 1 a8 first atom type atmnam 2 a8 second atom type central site atmnam 3 a8 third atom type key ad potential key See table 4 13 variable 1 real potential parameter see table 4 13 variable 2 real potential parameter see table 4 13 variable 3 real potential parameter see table 4 13 variable 4 real potential parameter see table 4 13 variable 5 real cutoff range for this potential The variables pertaining to each potential are described in table 4 13 Note that the fifth variable is the range at which the three body potential is truncated The distance is in measured from the central atom The specification of four body potentials is initiated by the directive fbp n CCLRC 121 where n is the number of four body potentials to be entered There follows n records each specifying a particular four body potential in the following manner atmnam 1 a8 first atom type central site atmnam 2 a8 second atom type atmnam 3 a8 third atom type atmnam 4 a8 fourth atom type key ad potential key See table 4 14 variable 1 real potential parameter see table 4 14 variable 2 real potential parameter see table 4 14 variable 3 real cutoff range for this potential A The variables pertaining to each potential are described in table 4 14 Note that the third variable is the range at which the four body potential is truncated The distance is in measured from the central atom
206. s 5X2 5 2311 2 Ti tir Pijkn wsl ri tpn Lij Den 2 57 Tij Formally the force on an atom arising from the inversion potential is given by o fe grg U Oijen 2 58 with being one of i j k n and a one of x y z This may be expanded into o 1 o Ore Brita Ei O dikn Pigen 8 rij gn rij Bum 1 y AAA AA 2 59 Or Tij Following through the extremely tedious differentiation gives the result 1 o cos Pijkn z che KAN fos Si da r p g 0 Lij Ue en Lij Ben On Tj y ga E x ra bg da 2 rij rij Ben Ue rij Lik rij Ben Lik Ben E UknTik Tik Li Oy e r r9 00 da A ri ES s kn gn Tij Tik T Lij Opa Lik Byn E UknT ik Tik Tuc Uy A N ro 5en q LR ls Lij cdi uns Lij Lin Lij diss Lin i3 UknTin Tin Tic Dr 7 Ea Es ro t 6s 5 LE ra a tij Den kn Lij Lin rij Dea Lin E23 UknTin Tin This general formula applies to all atoms i j k n It must be remembered however that these formulae apply to just one of the three contributing terms i e one angle of the full inversion potential specifically the inversion angle pertaining to the out of plane vector Tij The contributions arising from the other vectors r and r are obtained by the cyclic permutation of the indices in the manner described above All these force contributions must be added to the final atomic forces Formally t
207. s Valinomycin Molecule with 146 SPC Waters UNITS kcal MOLECULES 2 Valinomycin NUMMOLS 1 ATOMS 168 0 16 0000 0 4160 1 OS 16 0000 0 4550 1 HC 1 0080 0 0580 1 C 12 0100 0 4770 1 BONDS 78 harm 31 19 674 000 1 44900 harm 33 31 620 000 1 52600 harm 168 19 980 000 1 33500 harm 168 162 634 000 1 52200 CONSTRAINTS 90 20 19 1 000017 22 21 1 000032 166 164 1 000087 167 164 0 999968 ANGLES 312 harm 43 2 44 200 00 116 40 harm 69 5 TO 200 00 116 40 n n n n n n n n n n n n harm 18 168 162 160 00 120 40 harm 19 168 162 140 00 116 60 DIHEDRALS 371 harm 1 43 2 44 2 3000 180 00 harm 31 43 2 44 2 3000 180 00 CCLRC 111 cos 149 17 161 16 10 500 180 00 cos 162 19 168 18 10 500 180 00 FINISH SPC Water NUMMOLS 146 ATOMS 3 OW 16 0000 0 8200 HW 1 0080 0 4100 HW 1 0080 0 4100 CONSTRAINTS 3 1 2 1 0000 1 3 1 0000 2 3 1 63299 FINISH VDW 45 C C 1j 0 12000 3 2963 C CT 1j 0 08485 3 2518 n n n n n n n n n n n n n n OW 08 1j 0 15100 3 0451 08 OS 1j 0 15000 2 9400 CLOSE 4 1 3 1 Format The FIELD file is fixed formatted Integers are formatted as i5 reals as f12 0 and characters as a4 a8 a40 or a80 depending on context The contents of the file are variable and are defined by the use of directives Additional information is associated with the directives and is free formatted as in the CONTROL file above The file is not case
208. s potential type Variables 1 4 functional formt Electric field Oscillating Shear Continuous Shear Gravitational Field Magnetic Field Containing Sphere r gt Rew E A Ro r Chapter 5 DL_POLY_2 Examples 138 CCLRC 139 Scope of Chapter This chapter describes the standard test cases for DL_POLY_2 the input and output files for which are in the data sub directory CCLRC 140 5 1 DL POLY Examples 5 1 1 Test Cases The following example data sets both input and output are stored in the subdirectory data These are provided so that you may check that your version of DL_POLY is working correctly All the jobs are short and should require no more than a few minutes execution time even on a single processor computer The output files are stored in compressed format The test cases can be run by typing select n from the execute directory where n is the number of the test case The select macro will copy the appropriate CONTROL CONFIG and FIELD files to the execute directory ready for execution The output files OUTPUT REVCON and STATIS may be compared with the files supplied in the data directory The example output files provided in the data directory were obtained on 4 processors of an IBM SP 2 parallel system 120 MHz P2SC thin nodes The program was compiled with the three point interpolation option It should be noted that the potentials and the simulation conditions used in the following
209. s by scanning the DL POLY 2 input files CONTROL FIELD and CONFIG and then writing out a sample DL PARAMS INC file which has the name NEW PARAMS INC PARSET is not foolproof however The user must prepare the correct input files be forehand which can be difficult without the error checking the DL POLY 2 code affords Also because of the complexity of the requirements PARSET can only supply a reasonable CCLRC 90 estimate of some of the array dimensions and these may not be quite right for every case It will be reasonably close however Notwithstanding the limitations of PARSET its use as a labour saving device is recommended PARSET is described in detail in section 6 1 1 The program is found in the utility subdirectory 3 2 3 Running DL_POLY_2 To run the DL POLY 2 executable DLPOLY X you will initially require three possibly four input data files which you must create in the execute sub directory or whichever sub directory you keep the executable program The first of these is the CONTROL file section 4 1 1 which indicates to DL POLY 2 what kind of simulation you want to run how much data you want to gather and for how long you want the job to run The second file you need is the CONFIG file section 4 1 2 This contains the atom positions and depending on how the file was created e g whether this is a configuration created from scratch or the end point of another run the velocities also The third file re
210. s file requires the entire program to be recompiled The build directory contains example makefiles which do this automatically 4 The parameters to found in the params COMMON block versions 2 11 and above may be determined from the following FORTRAN extract taken from the DL PARAMS INC file The variables appearing have the same meaning as the parameters described above c array allocation parameters set by subroutine parset common params kmaxa kmaxb kmaxc minnode msatms msbad msgrp mspmf msteth mxangl mxatms mxbond mxbuff mxcell mxcons mxdihd mxewld mxexcl mxfbp mxfld mxgatm mxgrid mxgrp mxinv mxlist mxlshp mxneut mxngp mxnstk mxpang mxpbnd mxpdih mxpfbp mxpinv mxpmf mxproc mxptbp mxpvdw mxrdf mxshl mxsite mxspmf mxstak mxsvdw mxtang mxtbnd mxtbp mxtcon mxtdih mxteth mxtinv mxtmls mxtshl mxungp mxvdw mxxdf mx2tbp mx3fbp mxebuf mxquat mxshak bd bdi bd bd b b hM Bibliography 1 Smith W and Forester T 1996 J Molec Graphics 14 136 2 Smith W 1987 Molecular Graphics 5 71 3 van Gunsteren W F and Berendsen H J C 1987 Groningen Molecular Simu 11 12 13 14 15 16 17 lation GROMOS Library Manual BIOMOS Nijenborgh 9747 Ag Groningen The Netherlands Standard GROMOS reference Weiner S J Kollman P A Nguyen D T and Case D A 1986 J Comp Chem 7 230 Br nger A T 1992 X PLOR A System for X Ray Crystallography and NM
211. s follows the dimensions of array variables are given in brackets in terms of parameters from the DL_PARAMS INC file see section 7 1 1 record 1 nstep timestep of final configuration numacc number of configurations used in averages numrdf number of configurations used in rdf averages chit relaxation time of thermostat chip relaxation time of barostat conint conserved quantity for selected ensemble nzden number of configurations used in z density record 2 eta scaling factors for simulation cell matrix elements 9 record 3 stpval instantaneous values of thermodynamic variables mxnstk record 4 sumval average values of thermodynamic variables mxnstk record 5 ssqval fluctuation squared of thermodynamic variables mxnstk record 6 zumval running totals of thermodynamic variables mxnstk record 7 ravval rolling averages of thermodynamic variables mxnstk record 8 Stkval stacked values of thermodynamic variables mxstak xmxnstk record 9 xx0 atomic x coordinates at MSD time origin mxatms yy0 atomic y coordinates at MSD time origin mxatms zz0 atomic z coordinates at MSD time origin mxatms record 10 XXS instantaneous atomic x coordinates for MSD mxatms yys instantaneous atomic y coordinates for MSD mxatms ZZS instantaneous atomic z coordinates for MSD mxatms record 11 rdf Optional RDF array mxrdf xmxvdw record 12 zdens Optional z density array mxrdf xmxsvdw CCLRC 123 4 1 4
212. s for atomic sites However there are a series of utilities that will at least produce the CONNECT_DAT file for use with AMBFORCE We now outline these utilities and the order in which they should be used If you have a structure from the Cambridge Structural database CSDB then use the utility FRACCON to take fractional coordinate data and produce a CONNECT_DAT and ambforce dat file for use with AMBFORCE Note that you will need to modify FRACCON to get the AMBER names correct for sites in your molecule The version of FRACCON supplied with DL POLY 2 is specific to the valinomycin molecule If you require an all atom force field and the database file does not contain hydrogen positions then use the utility FRACFILL in place of FRACCON FRACCON produces an output file HFILL which should then be used as input for the utility HFILL The HFILL utility fills out the structure with the missing hydrogens Note that you may need to know what the atomic charges are in some systems for example the AMBER charges from the literature Note with minor modifications the utilities FRACFILL and FRACCON can be used on structures from databases other than the Cambridge structural database 3 3 3 Adding Solvent to a Structure The utility WATERADD adds water from an equilibrated configuration of 256 SPC water molecules at 300 K to fill out the MD cell The utility SOLVADD fills out the MD box with single site solvent molecules from a f c c lattice The FIELD f
213. s with bond constraints 2 5 3 2 Berendsen Thermostat In the Berendsen algorithm the instantaneous temperature is pushed towards the desired temperature by scaling the velocities at each step i At yy x T HER MY E OEA Zan 2 168 As with the Nos Hoover thermostat iteration is required to obtain self consistency of x v t and 7 although it should be noted x has different roles in the two thermostats The Berendsen algorithm conserves total momentum but not energy As with the Nos Hoover algorithm the presence of constraint bonds requires an addi tional iteration with one application of SHAKE corrections The algorithm is implemented in the DL_POLY routines NVT B0 and NVT Bl the latter being for systems with bond constraints 2 5 4 Gaussian Constraints Kinetic temperature can be made a constant of the equations of motion by imposing an additional constraint on the system If one writes the equations of motions as dr t _ x cow det M m EC 2 169 2 170 CCLRC 62 with the temperature constraint dT ad u Uu Stns ox omit f t 0 2 171 i then choosing 2 172 minimizes the least squares differences between the Newtonian and constrained tra jectories Following Brown and Clarke 36 the algorithm is implemented by calculating y 1 1 xAt 2 PIT Text A T t verlas e Q2 Da t 240 e sad PAD E r t At u t 2A 2 173 where 7 is obtained from standard Verlet leapfrog i
214. sed by DL POLY to help determine a working volume for the system This is needed to help calculate RDFs etc The working value of D is in fact taken as one of 3xcutoff or 2xmax abs Z coordinate cutoff or the user specified D whichever is the larger Note that the Ewald sum cannot be used with this boundary condition The surface in a system with charges can be modelled with DL POLY 2 however if periodicity is allowed in the Z direction In this case slabs of ions well separated by vacuum zones in the Z direction can be handled with IMCON 2 or 3 Hexagonal prism boundaries IMCON 7 In this case the Z axis lies along a line joining the centres of the hexagonal faces The Y axis is perpendicular to this and passes through the centre of one of the faces The X axis completes the orthonormal set and passes through the centre of an edge that is parallel to the Z axis Note It is important to get this convention right The origin of the atomic coordinates is the centre of the cell If the length of one of the hexagon edges is D the cell vectors required in the CONFIG file are 3D 0 0 0 4 3D 0 0 0 H where H is the prism height the distance between hexagonal faces The orthorhombic cell also defined by these vectors enscribes the hexagonal prism and possesses twice the volume but the height and the centre are the same The Ewald summation method may be used with this periodic boundary condition CCLRC 175 The he
215. shape and size of the simulation cell Briefly these are as follows which also indicates the IMCON flag defining the simulation cell type in the CONFIG File see 4 1 2 1 None e g isolated polymer in space IMCON 0 2 Cubic periodic boundaries IMCON 1 3 Orthorhombic periodic boundaries IMCON 2 4 Parallelepiped periodic boundaries IMCON 3 5 Truncated octahedral periodic boundaries IMCON 4 6 Rhombic dodecahedral periodic boundaries IMCON 5 7 Slab X Y periodic Z nonperiodic IMCON 6 8 Hexagonal prism periodic boundaries IMCON 7 We shall now look at each of these in more detail Note that in all cases the cell vectors and the positions of the atoms in the cell are to be specified in Angstroms No periodic boundary IMCON 0 Simulations requiring no periodic boundaries are best suited to in vacuuo simulations such as the conformational study of an isolated polymer molecule This boundary condition is not recommended for studies in a solvent since evaporation is likely to be a problem Note this boundary condition cannot be used with the Ewald summation method 170 CCLRC 171 Cubic periodic boundaries IMCON 1 The cubic MD cell The cubic MD cell is perhaps the most commonly used in simulation and has the advantage of great simplicity In DL_POLY_2 the cell is defined with the principle axes passing through the centres of the faces Thus for a cube with sidelengt
216. so that the reduced mass needs to be re evaluated every time step because it depends on the relative orienation of the two bodies Finally we note the algorithm reduces to the standard SHAKE algorithm if the rigid bodies are replaced by point atoms In such a case even though d is zero care must be taken to avoid the singularity arising from I 2 207 F const CCLRC 70 This linked rigid body algorithm is implemented in NVEQ_2 with the QSHAKE cor rections to the forces applied in QSHAKE Again it is straightforward to couple these systems to a Hoover type or Berendsen thermostat and or barostat The Hoover and Berendsen thermostated versions are found in NVTQ H2 and NVTQ_B2 respectively The isotropic con stant pressure implementations are found in NPTQ_H2 and NPTQ_B2 while the anisotropic constant pressure routines are found in NPTQ_H4 and NPTQ_B4 An outline of the parallel version of QSHAKE is given in section 2 6 8 2 5 7 The DL_POLY_2 Multiple Timestep Algorithm For simulations employing a large spherical cutoff reut in the calculation of the interactions DL_POLY_2 offers the possibility of using a multiple timestep algorithm to improve the efficiency The method is based on that described by Streett et al 38 39 with extension to Coulombic systems by Forester et al 40 In themultiple timestep algorithm there are two cutoffs for the pair interactions a relatively large cutoff rey which is used to define the stand
217. st o quench o rdf0 o rdf1 o A rdshake_1 o result o revive o scdens o shellsort o shlfrc o shlmerge o shlqnch o shmove o simdef o splice o static o strip o strucopt o sysdef o sysgen o systemp o sysbook o sysinit o V tethfrc o thbfrc o timchk o traject o vertest o vscaleg o warning o xscale o zden0 o zden1 o OBJ_SPME bspcoe o bspgen o cpy rtc o ele prd o ewald spme o Scl csum o set block o spl cexp o spme for o 0BJ NEU coulOneu o coul2neu o coul3neu o excludeneu o forcesneu o multipleneu o neutlst o parneulst o prneulst o V parlinkneu o rdfOneu o OBJ_RIG nptq bi o nptq_b2 o nptq_b3 o nptq_b4 o nptq h o nptq h2 0 nptq h3 o nptq h4 o nveq 1 0 nveq 2 0 nvtq_b1 o nvtq b2 0 nvtq hi o nvtq_h2 o passquat o qshake o quatbook o quatqnch o OBJ_RRR denloc o dihfrc o erfcgen o ewald2 o ewald4 o forgen o V fortab o metgen o srfrce o srfrceneu o suttchen o OBJ_4PT denloc_4pt o dihfrc 4pt o erfcgen o ewald2 4pt o ewald4_4pt o forgen o fortab o metgen o srfrce 4pt o srfrceneu 4pt o suttchen_4pt o OBJ_RSQ denloc_rsq o dihfrc rsq o erfcgen_rsq o ewald2_rsq o ewald4_rsq o forgen_rsq o fortab rsq o metgen_rsq o srfrce rsq o srfrceneu_rsq o suttchen_rsq o OBJ_EXT crecv o csend o gsync o mynode o nodedim o numnodes o TIMER etime o Define targets CCLRC 161 echo Error please specify a target machine echo Permissible targets for this Makefile are echo i echo alpha linux echo alpha linux
218. stances you may consider overriding this error message and continuing with your simulation For example if your simulation does not require the polarisability to be a feature of the rigid species but is confined to free atoms or flexible molecules in the same system The appropriate error trap is found in subroutine SYSDEF Message 95 error potential cutoff exceeds half cell width In order for the minimum image convention to work correctly within DL_POLY_2 it is necessary to ensure that the cutoff applied to the pair potentials does not exceed half the perpendicular width of the simulation cell The perpendicular width is the shortest distance between opposing cell faces Termination results if this is detected In NVE simulations this can only happen at the start of a simulation but in NPT it may occur at any time Action Supply a cutoff that is less than half the cell width If running constant pressure calcula tions use a cutoff that will accommodate the fluctuations in the simulation cell Study the fluctuations in the OUTPUT file to help you with this Message 97 error cannot use shell model with neutral groups The dynamical shell model was not designed to work with neutral groups This error results if an attempt is made to combine both CCLRC 192 Action There is no general remedy for this error if you wish to combine both these capabilities However if your simulation does not require the polarisability to be a fe
219. stant pressure simulations In DL_POLY_2 the frozen atom option is handled by the subroutine FREEZE 2 3 The Intermolecular Potential Functions In this section we outline the pair body three body and four body potential functions available in DL_POLY_2 An important distinction between these and intramolecular bond forces in DL_POLY_2 is that they are specified by atom types rather than atom indices 2 3 1 Short Ranged van der Waals Potentials The short ranged pair forces available in DL_POLY_2 are as follows U rs 5 z 2 70 ij ij 2MP S NS 3 n m potential 27 nm Eo To k To i U rij incom n 2 2 72 1 12 6 potential 12 6 2 Lennard Jones lj CCLRC 40 8 Buckingham potential buck PE U r A exp 42 2 73 rg T 2 73 Born Huggins Meyer potential bhm C D U rij A exp Blo ri 5 35 2 74 ij ij Hydrogen bond 12 10 potential hbnd U rij 5 ES 5 2 75 ij ij Shifted force n m potential 27 snm Etsi ex 2 2 ERGO em E D Ed E DR 3 m oy S S Di 3 P RES 2 nm NC 3 D S CR with y s 2 77 um aue T n m B 4 2 78 fe uu HG ng EE m y m 1 31 mp 1 n y n 1 7 This peculiar form has the advantage over the standard shifted n m potential in that both E and ro well depth and location of minimum retain their original meaning after the
220. t the job as if it had not been interrupted To restart a simulation after normal termination you will again require the CONTROL file the FIELD and TABLE file and a CONFIG file which is the exact copy of the REVCON file created by the previous job You will also require a new file REVOLD section 4 1 4 which is an exact copy of the previous REVIVE file If you attempt to restart DL_POLY_2 without this additional file available the job will fail Note that DL POLY 2 will append new data to the existing STATIS and HISTORY files if the run is restarted other output files will be overwritten In the event of machine failure you should be able to restart the job in the same way from the surviving REVCON and REVIVE files which are dumped at intervals to meet just such an emergency In this case check carefully that the input files are intact and use the HISTORY and STATIS files with caution there may be duplicated or missing records The reprieve processing capabilities of DL POLY 2 are not foolproof the job may crash while these files are being written for example but they can help a great deal You are advised to keep backup copies of these files noting the times they were written to help you avoid going right back to the start of a simulation You can also extend a simulation beyond its initial allocation of timesteps provided you still have the REVCON and REVIVE files These should be copied to the CONFIG and REVOLD files respectively
221. tants ie independent of distance at least beyond the range rey This allows the virial correction to be computed by the methods used in the short ranged potentials The result is Ne a NS mec a Nate ec 2npa 4 Gu Ta 2 Weorr 2npa fac E a 2 2 96 1 This correction may be used as it stands or with the further approximation N N 1 2 DR See un where pl P gt is regarded as a constant of the system In DL POLY 2 the metal forces are handled by the routine SUTTCHEN The local density is calculated by routines SCDENS and DENLOC The long range corrections are calculated by LRCMETAL 2 3 3 Three Body Potentials The three body potentials in DL POLY 2 are mostly valence angle forms They are primar ily included to permit simulation of amorphous materials e g silicate glasses However these have been extended to include the DREIDING 7 hydrogen bond The potential forms available are as follows 1 Truncated harmonic thrm U Ojia Ozin 0 exp r5 78 0 2 98 CCLRC 44 2 Screened Harmonic shrm k U Ojik 3 Ojik 0o exp ri p1 rix p 2 99 3 Screened Vessal 24 bvs1 k 2 2 U Ojik Sona Lt n Ojik 7 j exp rij p1 rix p2 2 100 4 Iruncated Vessal 25 bvs2 U Oji kl 054 Ajax 09 Ojik 00 2 QU Ojik 90 m 00 exp ri r amp 2 101 5 DREIDING hydrogen bon
222. te mxspmf mxstak mxsvdw mxtang mxtbnd mxtbp mxtcon mxtdih mxteth mxtinv mxtmls mxtshl mxungp mxvdw mxxdf nconf ndump nfield nhist nrdfdt nread nrest nrite nstats ntable nzdfdt pai 2 variable lt mxatms variable mxpang 1 5 variable variable variable vaiable variable variable variable variable variable variable mxvdw mxsvdw variable variable variable variable variable variable variable mxsvdw 1 mxsvdw 2 max mxlist msatms mxcons mxni mxn1i mxneut 1 2 8 variable 7 21 24 5 22 6 20 23 25 3 141592653589793 154 max number of inversion potential parameters number of atoms in potential of mean force constraints max number of nodes used in parallel constraint algorithm max number of 3 body potential parameters max number of van der Waals potential parameters max iterations in quaternion integration number of tabulation points for radial distribution functions max number of iterations in shake algorithm max number of core shell units max number of molecular sites max number sites to define pmf units dimension of stack arrays for rolling averages max number of different types of sites for pair potentials max number of different bond angle potentials max number of chemical bond potentials max number of 3 body potentials max number of specified bondlength constraints max number of different dihedral potentials max number of tethered a
223. ted Coulombic potential Reaction Field electrostatics keyfce 0 means no non bonded terms are evaluated i keyfce 1 means only short range potentials are evaluated CCLRC 4 1 2 The CONFIG File The CONFIG file contains the dimensions of the unit cell the key for periodic boundary conditions and the atomic labels coordinates velocities and forces This file is read by the subroutine SYSGEN It is also read by the subroutine SIMDEF if the ewald precision directive is used The first few records of a typical CONFIG file are shown below Icel structure 6x6x6 unit cells with proton disorder 2 3 26 988000000000000 13 494000000000000 O 000000000000000 OW 1 2 505228382 0 5446573999 3515 939287 HW 2 1 622622646 1 507099154 7455 527553 HW 3 3 258494716 2 413871957 7896 278327 OW 4 0 9720599243E 01 1 787340483 9226 455153 etc 4 1 2 1 Format The file is fixed formatted integers as i10 reals as 20 0 The header record is format 0 000000000000000 23 372293600000000 0 000000000000000 44 028000000000000 1 484234330 1 872177437 13070 74357 1 972916834 1 577400769 4806 880540 2 125627191 4 336956694 8318 045939 2 503798635 1 021777575 9445 662860 ted as 80 alphanumeric characters 4 1 2 2 Definitions of Variables record 1 header a80 record 2 levcfg integer imcon integer record 3 cell 1 real title line CONFIG file key See table 4 5 for p
224. ted Data Strategy oaoa Distributing the Intramolecular Bonded Terms Distributing the Nonbonded Terms Modifications for the Ewald Sum Three Body Forces 2 6n e o moy o a Metal Potentials i cm rc ue RR om RUE a ee es CCLRC 2 6 7 Summing the Atomic Forces o 00000 2 6 8 The RD SHAKE and Parallel QSHAKE Algorithms 3 DL_POLY_2 Construction and Execution 3 1 Constructing DL_POLY_2 sAN OVERVIEW e vns yv mL Ee Re 3 1 1 Constructing the Standard Version 2 4 3 1 2 Constructing Nonstandard Versions llle 3 2 Compiling and Running DL_POLY2 o o 3 241 Compiling the Source Code lll 3 2 2 Assisting Compilation with the Utility Program PARSET 3 2 Running DE POLY 2 25 5 2 3 eye ox bos R3 3 pex Gee kbe d ae 3 2 4 Restarting DL PO LY De ue ue igo a ce de IE FUR ue es Ead 3 3 A Guide to Preparing Input Files lll leen 3 3 1 Inorganic Materials 2l 3 3 2 Macromolecules 3 3 3 Adding Solvent to 3 3 4 Analysing Results a otruct re e So edad hy ke els PAS exe 3 3 5 Choosing Ewald Sum Variables 3 4 DL_POLY_2 Error Proces 3 4 1 The DL_POLY_2 I 4 DL_POLY_2 Data Files 41 The INPUT files 4 1 1 The CONTROL F 4 12 The CONFIG File 4 1 3 The FIELD File SING e a aa Ge ew ok nternal Error Facility Meu e O E Mite Oh te ak Ms O
225. tep algorithm CCLRC 203 Message 386 error primary cutoff larger than rcut The primary cutoff specified by the prim directive in the CONTROL file exceeds the value specified for the forces cutoff directive cut Applies only if the multiple timestep option is required Action Locate the prim directive in the CONTROL file and alter the chosen cutoff Alternatively increase the real space cutoff specified with the cut directive Take care to avoid error number 398 Message 387 error system pressure not specified The target system pressure has not been specified in the CONTROL file Applies to NPT simulations only Action Insert press directive in the CONTROL file specifying the required system pressure Message 388 error npt incompatible with multiple timestep The use of NPT constant pressure and temperature is not compatible with the multiple timestep option Action Simulation must be run at fixed volume in this case But note it may be possible to use NPT without the multiple timestep in ourder to estimate the required system volume then switch back to multiple timestep and NVT dynamics at the required volume Message 390 error npt ensemble requested in non periodic system A non periodic system has no defined volume hence the NPT algorithm cannot be applied Action Either simulate the system with a periodic boundary or use another ensemble Message 392 error too many link cells requested Th
226. terval It is readily apparent how this scheme can lead to a significant saving in execution time Extension of this basic idea to simulations using the Ewald sum requires the following 1 the reciprocal space terms are calculated only for the first two timesteps of the multi step 2 the contribution to the reciprocal space terms arising from primary interactions are immediately subtracted leaving only the long range components This is done in real space by subtracting erf terms 3 the real space Coulombic forces arising from the secondary atoms are calculated in CCLRC 71 the first two timesteps of the multi step using the normal Ewald expressions i e the erfc terms 4 the Coulombic forces arising from primary atoms are calculated at every timestep in real space assuming the full Coulombic force In this way the Coulombic forces can be handled by the same multiple timestep scheme as the van der Waals forces The algorithm is described in detail in 40 Note that the accuracy of the algorithm is a function of the multi step interval multt and decreases as multt increases Also the algorithm is non symplectic i e it is not time reversible and is therefore susceptible to energy drift Its use with a thermostat is therefore advised dius Tprim and secondary if outside this radius but within freut Interactions arising from primary atoms are evaluated every tim 2 5 8 The DL POLY 2 RESPA Multiple Timestep Implementat
227. test cases are chosen to demonstrate functionality only They are not necessarily ap propriate for serious simulation of the test systems Note also that the DL_POLY_2 Graphical User Interface 20 provides a convenient means for running and viewing these test cases 5 1 1 1 Test Case 1 KNaSiz0O5 Potassium Sodium disilicate glass NaKSi205 using two and three body potentials Some of the two body potentials are read from the TABLE file Electrostatics are handled by a multiple timestep Ewald sum method Cubic periodic boundaries are in use 5 1 1 2 Test Case 2 Metal simulation with Sutton Chen potentials FCC Aluminium using Sutton Chen potentials Temperature is controlled by the method of Gaussian constraints 5 1 1 3 Test Case 3 An antibiotic in water Valinomycin in 1223 spc water molecules The temperature is controlled by a Nos Hoover thermostat while electrostatics are handled by a shifted Coulombic potential The water is defined as a rigid body while bond constraints are applied to all chemical bonds in the valinomycin Truncated octahedral boundary conditions are used 5 1 1 4 Test Case 4 Shell model of water 256 molecules of water with a polarizable oxygen atom Temperature is controlled by the Berendsen thermostat while electrostatics are handled by the reaction field method with CCLRC 141 a charge group cutoff scheme Slab period boundary conditions are used The water molecule apart from the shell is t
228. tet line 3 cpu s volume temp shl eng shl vir_shl alpha beta gamma vir_pmf press MD step number total internal energy of the system system temperature configurational energy of the system configurational energy due to short range potentials configurational energy due to electrostatic potential configurational energy due to chemical bond potentials configurational energy due to valence angle and three body potentials configurational energy due to dihedral inversion and four body potentials configurational energy due to tethering potentials elapsed simulation time ps since the beginning of the job enthalpy of system rotational temperature total configurational contribution to the virial short range potential contribution to the virial electrostatic potential contribution to the virial chemical bond contribution to the virial angular and three body potentials contribution to the virial constraint bond contribution to the virial tethering potential contribution to the virial elapsed cpu time since the beginning of the job system volume core shell temperature configurational energy due to core shell potentials core shell potential contribution to the virial angle between b and c cell vectors angle between c and a cell vectors angle between a and b cell vectors Potential of mean force constraint contribution to the virial pressure Note The total internal energy of the system variable tot_energy includes
229. the appropriate library directories are included in the C preprocessing flags CPPFLAGS If you intend the program for a single processor machine use the flag DSERIAL see the sun example in the makefile 2 Enabling the Smooth Particle Mesh Ewald Users of DL_POLY_2 Version 2 12 and above should note that modifications to the makefile may be required if the code is automatically to incorporate the Smooth Particle Mesh Ewald SPME Primarily this requires a specification of the system li brary location of the 3D Fast Fourier Transform FFT routine implicit in the method The default FFT routine for DL_POLY_2 is the public domain code FFTW but this is not specified for all platforms represented in the makefile The user who wishes to use the SPME feature should check the relevant part of the makefile to make sure this is enabled this is generally made clear in the makefile comments The SPME feature is enabled by setting the parameter FFTW_LIBRARY to specify the location of the FFTW software and by inserting the flag DFFTW in the CPFLAGS list see above Note that for most parallel systems represented in the makefile the appro priate FFT is already enabled which is usually not FFTW This is particularly the case for Cray T3E IBM SP 2 and parallel SGI machines 3 MPI and PVM implementations The implementation of MPI may differ between sites On some systems the For tran callable subroutine names are expected to end with an un
230. the code required if necessary by amending subroutines SYSDEF and FBPFRC Message 444 error undefined bond potential DL POLY 2 has been requested to process a bond potential it does not recognise Action Check the FIELD file and make sure the keyword is correctly defined Make sure that subroutine BNDFRC contains the code necessary to deal with the requested potential Add the code required if necessary by amending subroutines SYSDEF and BNDFRC Message 446 error undefined electrostatic key in dihfrc The subroutine DIHFRC has been requested to process a form of electrostatic potential it does not recognise Action The error arises because the integer key keyfrc has an inappropriate value which should not happen in the standard version of DL POLY 2 Check that the FIELD file correctly specifies the potential Make sure the version of DIHFRC does contain the potential you are specifying Report the error to the authors if these checks are correct Message 448 error undefined dihedral potential A form of dihedral potential has been requested which DL POLY 2 does not recognise Action Locate the offending potential in the FIELD file and remove Replace with one acceptable to DL POLY 2 if this is reasonable Alternatively you may consider defining the required potential in the code yourself Amendments to subroutines SYSDEF and DIHFRO and its variants will be required Message 449 error undefined inversion potential
231. tine COUL1 A further refinement of this approach is to truncate the 1 r potential at rey and add a linear term to the potential in order to make both the energy and the force zero at the cutoff The potential is thus GG l rij 2 U rj 2 120 ig 4T 0 E TA I l with the force on atom j given by qid 1 1 l E 2 121 I 4meo E i Tij with the force on atom i the negative of this This removes the heating effects that arise from the discontinuity in the forces at the cutoff in the simple truncated and shifted potential The physics of this potential however are little better It is only recommended for very crude structure optimizations CCLRC 49 The contribution to the atomic virial is which is not the negative of the potential term The contribution to be added to the atomic stress tensor is given by ger ese gr 2 123 where q B are x y z components The atomic stress tensor is symmetric In DL POLY 2 these forces are handled by the routine COULA 2 4 4 Coulomb Sum with Distance Dependent Dielectric This potential attempts to address the difficulties of applying the direct Coulomb sum without the brutal truncation of the previous case It hinges on the assumption that the electrostatic forces are effectively screened in real systems an effect which is approximated by introducing a dielectic term that increases with distance The interatomic potential for two charged ions is
232. tion tables A complication in the construction of the Verlet neighbour list for macromolecules is the concept of excluded atoms which arises from the need to exclude certain atom pairs from the overall list Which atom pairs need to be excluded is dependent on the precise CCLRC 27 nature of the force field model but as a minimum atom pairs linked via extensible bonds or constraints and atoms grouped in pairs linked via valence angles are probable candi dates The assumption behind this requirement is that atoms that are formally bonded in a chemical sense should not participate in nonbonded interactions However this is not a universal requirement of all force fields The same considerations are needed in dealing with charged excluded atoms DL_POLY_2 has several subroutines available for constructing the Verlet neighbour list while taking care of the excluded atoms see chapters 3 and 7 for further information Three and four body nonbonded forces are assumed to be short ranged and therefore calculated using the link cell algorithm 23 They ignore the possibility of there being any excluded interactions involving the atoms concerned Throughout this section the description of the force field assumes the simulated system is described as an assembly of atoms This is for convenience only and readers should understand that DL_POLY_2 does recognise molecular entities defined either through con straint bonds or rigid bodies In the case
233. to the core shell units but this should should not amount to more than a few percent of the total kinetic energy The calculation of the virial and stress tensor in this model is based on that for a diatomic molecule with charged atoms The electrostatic and short ranged forces are cal culated as described above The forces of the harmonic springs are calculated as described for intramolecular harmonic bonds The relationship between the kinetic energy and the temperature is different however as the core shell unit is permitted only three translational degrees of freedom and the degrees of freedom corresponding to rotation and vibration of the unit are discounted the kinetic energy of these is regarded as zero In DL POLY 2 the shell forces are handled by the routine SHLFRC The kinetic en ergy is calculated by CORSHL and the routine SHQNCH performs the temperature scaling The dynamical shell model is used in conjunction with the methods for long range forces described above CCLRC 56 2 5 Integration algorithms DL_POLY integration algorithms are based around the Verlet leapfrog scheme which is both simplectic time reversible and simple in nature 10 It generates trajectories in the microcanonical NVE ensemble in which the total energy kinetic plus potential energy is conserved If this property drifts or fluctuates significantly in the course of a simulation it indicates that the timestep is too large or the potential cutoffs to
234. tom potentials max number of inversion potentials max number of molecule types max number of core shell unit types max number unique rigid body units max number of different pair potentials x2 if Sutton Chen potentials used max number of atoms in xdf ydf and zdf arrays mxn1 is number of sites in largest neutral group configuration file input channel data dumping interval in event of system crash force field input channel trajectory history file channel output channel for RDF data main input channel output channel accumulators restart dump file main output channel statistical data file output channel tabulated potentials file input channel output channel for Z density data file T CCLRC 155 prsunt 1 63842151d 1 pressure conversion factor r4pieO 138935 4835 electrostatic conversion factor i e unit charge 2 4 pi eps0 unit length unit energy sqrpi 1 7724538509055159 square root of m 7 1 1 4 Comments 1 A working version of the parameters file for DL POLY 2 versions prior to 2 11 for any given application can be constructed with the aid of the utility program PARSET see section 6 1 1 of the DL POLY 2 Reference Manual 2 Many of the above parameters refer to array dimensions If the application does not use the associated functionality these parameters may be set to 1 e g mxtang and mxangl may both be set to 1 if the simulation does not require bond angles 3 Any changes made to the parameter
235. tyle and it is adequately documented OCCLRC 2 DISCLAIMER Neither the CCLRC EPSRC CCP5 nor any of the authors of the DL POLY 2 package or its derivatives guarantee that the package is free from error Neither do they accept responsibility for any loss or damage that results from its use Use of the DL POLY 2 package without charge is confined to academic research only Commercial use is only permissible following negotiation with Daresbury Laboratory Users are not entitled to redistribute the program to third parties CCLRC 3 ACKNOWLEDGEMENTS DL_POLY_2 was developed under the auspices of the Council for the Central Laboratory of the Research Councils the Engineering and Physical Sciences Research Council and the former Science and Engineering Research Council under grants from the Computational Science Initiative and the Science and Materials Computing Committee The package is the property of the Council for the Central Laboratory of the Research Councils of the United Kingdom Advice assistance and encouragement in the development of DL_POLY_2 has been given by many people We gratefully acknowledge the following D Tildesley M J Gillan J Goodfellow D Fincham M Rodger W C Mackrodt J H R Clarke D Brown S Price P J Durham P Sherwood G D Price S C Potter Melchionna F M ller Plathe G Ciccotti M W Smith A Simpson J Geronowicz the HPCI Materials Consortium the Edinburgh Parallel Computing C
236. u are a DL POLY 2 user but not on this list you may request to be added Contact w smith dl ac uk 2 dl_poly_mail is a group list which is available to DL_POLY_2 users by request Its purpose is to allow DL_POLY_2 users to broadcast information and queries to each other To subscribe to this list send a mail message to majordomo dl ac uk with the one line message subscribe dl poly mail Subsequent messages may be broadcast by e mailing to the address dl poly mailQdl ac uk Chapter 2 DL POLY 2 Force Fields and Algorithms CCLRC 24 Scope of Chapter This chapter describes the interaction potentials and simulation algorithms coded into DL_POLY 2 CCLRC 25 2 1 The DL_POLY 2 Force Field The force field is the set of functions needed to define the interactions in a molecular system These may have a wide variety of analytical forms with some basis in chemical physics which must be parameterised to give the correct energy and forces A huge variety of forms is possible and for this reason the DL_POLY_2 force field is designed to be adaptable While it is not supplied with its own force field parameters many of the functions familiar to GROMOS 3 DREIDING 7 and AMBER 4 users have been coded in the package as well as less familiar forms In addition DL_POLY_2 retains the possibility of the user defining additional potentials In DL_POLY_2 the total configuration energy of a molecular system may be written as Noond
237. ude file 6 1 1 6 Comments PARSET does not undertake any error checking of the CONTROL FIELD and CONFIG files Any errors in these files will result in an incorrect parameters file It must also be recognised that for some of the parameters there is no straightforward formula for calculating suitable values from the input files In these cases the parameters produced represent a reasonable estimate only Fortunately these cases are few in number and as a rule PARSET will significantly reduce the time needed to prepare a working version of DL POLY 2 It is useful to prepare the input files assuming the largest simulation you are likely to attempt on a given system This will generate the largest executable necessary to prevent you having to recompile the code in the course of your study CCLRC 147 6 1 2 Useful Macros 6 1 2 1 Macros Macros are simple executable files containing standard unix commands A number of the are supplied with DL_POLY and are found in the execute sub directory The available macros are as follows e cleanup e copy gopoly e select e store The function of each of these is described below It is worth noting that most of these functions can be perfomed by the DL POLY 2 GUI 20 6 1 2 2 cleanup cleanup removes several standard data files from the execute sub directory It contains the unix commands rm OUTPUT REVCON REVOLD STATIS REVIVE gopoly and removes the files OUTPUT REVCON REVOLD STATIS
238. ulated potentials presented in the TABLE file have an increment that is greater than that used to define the other potentials in the simulation Ideally the increment should be rey magrid 4 where Teut is the potential cutoff for the short range potentials and mxgrid is the parameter defining the length of the interpolation arrays An increment less than this is permissible however Action The tables must be recalculated with an appropriate increment Message 23 error incompatible FIELD and TABLE file potentials This error arises when the specification of the short range potentials is different in the FIELD and TABLE files This usually means that the order of specification of the poten tials is different When DL_POLY_2 finds a change in the order of specification it assumes that the user has forgotten to enter one Action Check the FIELD and TABLE files Make sure that you correctly specify the pair potentials in the FIELD file indicating which ones are to be presented in the TABLE file Then check the TABLE file to make sure all the tabulated potentials are present in the order the FIELD file indicates Message 24 error end of file encountered in TABLE file This means the TABLE file is incomplete in some way either by having too few potentials included or the number of data points is incorrect Action Examine the TABLE file contents and regenerate it if it appears to be incomplete If it look intact check that the nu
239. uplication in the FIELD file and rectify Message 16 error strange exit from FIELD file processing This should never happen However one remote possibility is that there are more than 10 000 directives in the FIELD file It simply means that DL_POLY_2 has ceased pro cessing the FIELD data but has not reached the end of the file or encountered a close directive Probable cause corruption of the DL_POLY_2 executable or of the FIELD file We would be interested to hear of other reasons Action Recompile the program or recreate the FIELD file If neither of these works send the problem to us Message 17 error strange exit from CONTROL file processing See notes on message 16 above Message 18 error duplicate 3 body potential specified DL_POLY_2 has encountered a repeat specification of a 3 body potential in the FIELD file Action Locate the duplicate entry remove and resubmit job Message 19 error duplicate 4 body potential specified A 4 body potential has been duplicated in the FIELD file CCLRC 181 Action Locate the duplicated 4 body potential and remove Resubmit job Message 20 error too many molecule sites specified DL_POLY_2 has a fixed limit on the number of unique molecular sites in any given simu lation If this limit is exceeded the program terminates Action Standard user response Fix parameter mxsite Message 22 error unsuitable radial increment in TABLE file This arises when the tab
240. ve to FIELD file and resubmit Message 7 error energy unit respecified DL POLY 2 expects only one units directive in the FIELD file This error results if it encounters another implying an ambiguity in units Action Locate extra units directive in FIELD file and remove Message 8 error time step not specified DL POLY 2 requires a timestep directive in the CONTROL file This error results if none is encountered CCLRC 179 Action Inserttimestep directive in CONTROL file with an appropriate numerical value Message 10 error too many molecule types specified DL_POLY_2 has a set limit on the number of kinds of molecules it will handle in any sim ulation this is not the same as the number of molecules If this permitted maximum is exceeded the program terminates The error arises when the molecules directive in the FIELD file specifes too large a number Action Standard user response Fix parameter mxtmls Message 11 error duplicate molecule directive in FIELD file The number of different types of molecules in a simulation should only be specified once If DL_POLY_2 encounters more than one molecules directive it will terminate execution Action Locate the extra molecule directive in the FIELD file and remove Message 12 error unknown molecule directive in FIELD file Once DL POLY 2 encounters the molecules directive in the FIELD file it assumes the following records will supply data describing the
241. verage number of atoms of type b within a sphere of radius r around an atom of type a Note that a readable version of these data is provided by the RDFDAT file below CCLRC 131 4 2 2 9 Z Density Profile If both calculation and printing of Z density profiles has been requested by selecting direc tives zden and print rdf in the CONTROL file Z density profiles are printed out as the last part of the OUTPUT file This is written by the subroutine ZDEN1 First the number of time steps used for the collection of the histograms is stated Then each function is given in turn For each function a header line states the atom type represented by the function Then z p z and n z are given in tabular form Output is given from Z L 2 L 2 where L is the length of the MD cell in the Z direction and p z is the mean number density n z is the running integral from L 2 to z of xy cell area p s ds Note that a readable version of these data is provided by the ZDNDAT file below 4 2 3 The REVCON File This file is formatted and written by the subroutine REVIVE REVCON is the restart configuration file The file is written every ndump time steps in case of a system crash during execution and at the termination of the job A successful run of DL_POLY_2 will always produce a REVCON file but a failed job may not produce the file if an insufficient number of timesteps have elapsed ndump is a parameter defined in the DL_PARAMS INC file
242. very rarely The point of failure is in the SPLICE routine which is part of the RD SHAKE algorithm Action Standard user response Fix the parameter mxbuff CCLRC 198 Message 200 error rdf buffer array too small in revive This error indicates that the buffer array used to globally sum the rdf arrays in subroutine REVIVE is too small Action Standard user response Fix the parameter mxbuff Alternatively mxrdf can be set smaller Message 220 error too many neutral groups in system DL POLY 2 has a fixed limit on the number of charged groups in a simulation This error results if the number is exceeded Action Standard user response Fix the parameter mxneut Message 230 error neutral groups improperly arranged In the DL_PPOLY_2 FIELD file the charged groups must be defined in consecutive order This error results if this convention is not adhered to Action The arrangement of the data in the FIELD file must be sorted All atoms in the same group must be arranged consecutively Note that reordering the file in this way implies a rearrangement of the CONFIG file also Message 250 error Ewald sum requested with neutral groups DL_POLY_2 will not permit the use of neutral groups with the Ewald sum This error results if the two are used together Action Either remove the neut directive from the FIELD file or use a different method to evaluate the electrostatic interactions Message 260 error parameter
243. well the makefile will combine the object code with the system libraries and produce the executable 3 2 1 1 Keywords for the Makefile 1 TARGET The TARGET keyword indicates which kind of computer the code is to be com piled for This must be specifed there is no default value Valid targets can be listed by the makefile if the command make is typed without arguments The list CCLRC 86 frequently changes as more targets are added and redundant ones removed Users are encouraged to extend the Makefile for themselves using existing targets as examples 2 STRESS The STRESS keyword activates the code that calculates the stress tensor in the DL_POLY_2 code The arguments are e NOSTRESS if the stress tensor is not required e STRESS if the stress tensor is required default Calculation of the stress tensor is essential if constant stress Rahman Parrinello MD is required 3 TYPE The TYPE keyword creates variants of the DL_POLY_2 code which determine which scheme is to be used for the interpolation of the short range potential and force arrays The arguments are e 3pt compile with 3 point interpolation default e pt compile with 4 point interpolation e rsq compile with r interpolation A discussion of the merits of the different interpolation methods is given below section 3 2 1 3 4 EX The EX keyword specifies the executable name The default name for the executable is DLPOLY X 5
244. will be required Message 453 error four body potential cutoff undefined The cutoff radius for a four body potential has not been defined in the FIELD file Action Locate the offending four body force potential in the FIELD file and add the required cut off Resubmit the job CCLRC 211 Message 454 error undefined external field A form of external field potential has been requested which DL_POLY_2 does not recognise Action Locate the offending potential in the FIELD file and remove Replace with one acceptable to DL_POLY_2 if this is reasonable Alternatively you may consider defining the required potential in the code yourself Amendments to subroutines SYSDEF and EXTNFLD will be required Message 456 error core and shell in same rigid unit It is not sensible to fix both the core and the shell of a polarisable atom in the same molec ular unit Consequently DL_POLY_2 will abandon the job if this is found to be the case Action Locate the offending core shell unit there may be more than one in your FIELD file and release the shell preferably from the rigid body specification Message 458 error too many PMF constraints param mspmf too small The number of constraints in the potential of mean force is too large The dimensions of the appropriate arrays in DL_POLY_2 must be increased Action Standard user response Fix the parameter mspmf Message 460 error too many PMF sites parameter mxspmf too sm
245. without this being specified Action Supply a cutoff value for the van der Waals terms in the CONTROL file using the directive rvdw and resubmit job Message 410 error cell not consistent with image convention The simulation cell vectors appearing in the CONFIG file are not consistent with the spec ified image convention CCLRC 205 Action Locate the variable imcon in the CONFIG file and correct to suit the cell vectors Message 412 error mxxdf parameter too small for shake routine In DL POLY 2 the parameter mxxdf must be greater than or equal to the parameter mxcons If it is not this error is a possible result Action Standard user response Fix the parameter mxxdf Message 414 error conflicting ensemble options in CONTROL file DL_POLY_2 has found more than one ensemble directive in the CONTROL file Action Locate extra ensemble directives in CONTROL file and remove Message 416 error conflicting force options in CONTROL file DL_POLY_2 has found incompatible directives in the CONTROL file specifying the elec trostatic interactions options Action Locate the conflicting directives in the CONTROL file and correct Message 418 error bond vector work arrays too small in bndfrc The work arrays in BNDFRC have been exceeded Action Standard user response Fix the parameter msbad Message 419 error bond vector work arrays too small in angfrc The work arrays in ANGFRC have been exceeded
246. x the parameter mxbuff Message 426 error neutral groups not permitted with all pairs DL_POLY_2 will not permit simulations using both the neutral group and all pairs options together CCLRC 207 Action Switch off one of the conflicting options and rerun Message 427 error bond vector work arrays too small in invfrc The work arrays in subroutine INVFRC have been exceeded Action Standard user response Fix the parameter msbad Message 430 error integration routine not available A request for a nonexistent ensemble has been made or a request with conflicting options that DL POLY 2 cannot deal with e g a Evans thermostat with rigid body equations of motion Action Examine the CONTROL and FIELD files and remove inappropriate specifications Message 432 error intlist failed to assign constraints If the required simulation has constraint bonds DL_POLY_2 attempts to apportion the molecules to processors so that if possible there are no shared atoms between processors If this is not possible one or more molecules may be split between processors This message indicates that the code has failed to carry out either of these successfully Action The error may arise from a compiler error Try recompiling INTLIST without the optimiza tion flag turned on If the problem persists it should be reported to the authors after checking the input data for inconsistencies Message 433 error specify rcut before the
247. xagonal MD cell This MD cell is particularly suitable for simulating strands or fibres i e systems with a pronounced anisotropy in the Z direction such as DNA strands in solution or stretched polymer chains Appendix C DL_POLY Error Messages and User Action Introduction In this appendix we document the error messages encoded in DL_POLY_2 and the rec ommended user action The user response to these messages is different according to which version of the code is being run Versions preceding DL_POLY_2 version 2 11 are significantly different from those appearing after This is primariliy because version 2 11 intriduced FORTRAN 90 dynamic array allocation which greatly simplifies the use of the code but requires a different form of user intervention when array boundaries are vio lated The correct response is described as the standard user response in the approriate sections below to which the user should refer before acting on the error encountered The reader should also be aware that some of the error messages listed below may be either disabled in or absent from the installed version of DL POLY 2 Disabled messages generally apply to older releases of the code while missing messages apply to newer versions of the code and will not usually apply to previous releases They are all included for completeness Note that the wording of some of the messages may also have changed over time usually to provide more specific information
248. y a limited number of dihedral angles in the FIELD file and will terminate if too many are present Do not confuse this error with that described by message 61 below Action Standard user response Fix the parameter mxtdih Message 61 error too many dihedral angles in system The number of dihedral angles in the whole simulated system is limited by DL_POLY_2 Termination results if too many are encountered Do not confuse this error with that described by message 60 above Action Standard user response Fix the parameter mxdihd CCLRC 187 Message 62 error too many tethered atoms specified DL_POLY_2 will accept only a limited number of tethered atoms in the FIELD file and will terminate if too many are present Do not confuse this error with that described by message 63 below Action Standard user response Fix the parameter mxteth Message 63 error too many tethered atoms in system The number of tethered atoms in the simulated system is limited by DL_POLY_2 Termi nation results if too many are encountered Do not confuse this error with that described by message 62 above Action Standard user response Fix the parameter msteth Message 65 error too many excluded pairs specified This error can arise when DL_POLY_2 is identifying the atom pairs that cannot have a pair potential between them by virtue of being chemically bonded for example see subroutine EXCLUDE Some of the working arrays used
249. y the presence of the constraint force and torque will mean the positions and velocities of the remaining sites in the rigid body will also have to be corrected We proceed by seeking an approzimation to Fong then reintegrating the rigid body equations of motion with the improved total forces and torques on the body A few iterations are normally sufficient to achieve convergence If we assume the bond distance r is large in comparison to the correction then after the correction is made the bond length is pF V o Az Az A I 2r Azy Azi As YA Ie 2r Az 2 204 2 205 Q where AZ J bodies ATT Axl and Az J podies Az Thus a first order correction to the position of the constrained site is Ag Agrt Ag A4 const a E d xe xd e j 2 206 where e is the unit vector Fyonst Econst The term in the defines an effective mass M where 1 M 1 M 17 d x e x d e The effective reduced mass for the two linked bodies a and b is y MaM5 Ma Ms As in the standard SHAKE algorithm the reduced mass can then be used to predict the constraint force p r r A 2r Note that each prediction of the constraint force requires the rigid body equations of motion to be reintegrated accurately If two bodies are linked by one constraint bond only two or three iterations are necessary for convergence However convergence may be slower if an extended network of linked bodies is involved Note al
250. ystem and KE the kinetic energy at time t The full selection of integrration algorithms within DL POLY 2 is as follows NVE O Verlet leapfrog NVE 1 Verlet leaprog with RD SHAKE CCLRC 57 NVEQ_1 Rigid units with FIQA and RD SHAKE NVEQ 2 Linked rigid units with QSHAKE NVT_B0 Constant T Berendsen 14 with Verlet leapfrog NVT Bl Constant T Berendsen 14 with RD SHAKE NvT_EO Constant T Evans 15 with Verlet leapfrog NVT El Constant T Evans 15 with RD SHAKE NVT_HO Constant T Hoover 16 with Verlet leapfrog NVT_H1 Constant T Hoover 16 with RD SHAKE NVTQ_B1 Constant T Berendsen 14 with FIQA and RD SHAKE NVTQ B2 Constant T Berendsen 14 with QSHAKE NVTQ Hl Constant T Hoover 16 with FIQA and RD SHAKE NVTQ H2 Constant T Hoover 16 with QSHAKE NPT_BO Constant T P Berendsen 14 with Verlet leapfrog NPT Bl Constant T P Berendsen 14 with FIQA and RD SHAKE NPT B3 Constant T c Berendsen 14 with RD SHAKE NPT_HO Constant T P4 Hoover 16 with Verlet leapfrog NPT Hl Constant T P Hoover 16 with RD SHAKE NPT H3 Constant T c Hoover 16 with RD SHAKE NPTQ_B1 Constant T P Berendsen 14 with FIQA and RD SHAKE NPTQ B2 Constant T P Berendsen 14 with QSHAKE NST BO0 Constant T c Berendsen 14 with Verlet leapfrog NST_HO Constant To Hoover 16 with Verlet leapfrog NPTQ B3 Constant T c Berendsen 14 with FIQA and RD SHAKE NPTQ B4 Constant T c Berendsen 14 with QSHAKE NPTQ Hl Constant

THE DL POLY 2 USER MANUAL W. Smith and T.R. Forester

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