| /*************************************************************************/ |
| /* */ |
| /* Copyright (c) 1994 Stanford University */ |
| /* */ |
| /* All rights reserved. */ |
| /* */ |
| /* Permission is given to use, copy, and modify this software for any */ |
| /* non-commercial purpose as long as this copyright notice is not */ |
| /* removed. All other uses, including redistribution in whole or in */ |
| /* part, are forbidden without prior written permission. */ |
| /* */ |
| /* This software is provided with absolutely no warranty and no */ |
| /* support. */ |
| /* */ |
| /*************************************************************************/ |
| |
| EXTERN_ENV |
| #include <stdio.h> |
| #include <math.h> |
| |
| |
| #include "parameters.h" |
| #include "mdvar.h" |
| #include "water.h" |
| #include "wwpot.h" |
| #include "cnst.h" |
| #include "mddata.h" |
| #include "global.h" |
| |
| void SYSCNS() /* sets up some system constants */ |
| { |
| TSTEP=TSTEP/UNITT; /* time between steps */ |
| NATMO=NATOMS*NMOL; /* total number of atoms in system */ |
| NATMO3=NATMO*3; /* number of atoms * number of spatial dimensions */ |
| FPOT= UNITM * pow((UNITL/UNITT),2.0) / (BOLTZ*TEMP*NATMO); |
| FKIN=FPOT*0.50/(TSTEP*TSTEP); |
| |
| /* computed length of the cubical "box". Note that box size is |
| * computed as being large enough to handle the input number of |
| * water molecules |
| */ |
| |
| BOXL= pow( (NMOL*WTMOL*UNITM/RHO),(1.00/3.00)); |
| |
| /* normalized length of computational box (in Angstroms) */ |
| |
| BOXL=BOXL/UNITL; |
| |
| /* # of boxes per side */ |
| |
| BOXH = BOXL*0.50; |
| |
| /* set cutoff radius if it was not already read in nonzero from |
| the input file in water.C. If it was defined in the input file, |
| then that definition is retained. */ |
| |
| if (CUTOFF == 0.0) { |
| CUTOFF=max(BOXH,CUTOFF); /* cutoff radius is max of BOXH |
| and default (= 0); i.e. CUTOFF |
| radius is set to half the normalized |
| box length */ |
| } |
| |
| if (CUTOFF > 11.0) CUTOFF = 11.0; /* cutoff never greater than 11 |
| Angstrom */ |
| |
| BOX_PER_SIDE = ( BOXL / CUTOFF); |
| |
| /* BOX_PER_SIDE is always >=1 */ |
| if (!BOX_PER_SIDE) BOX_PER_SIDE = 1; |
| |
| /* Length of a box in Angstroms */ |
| |
| BOX_LENGTH = BOXL / ( (double) BOX_PER_SIDE); |
| |
| BPS_SQRD = BOX_PER_SIDE * BOX_PER_SIDE; |
| |
| NumBoxes = BOX_PER_SIDE * BOX_PER_SIDE * BOX_PER_SIDE; |
| |
| REF1= -QQ/(CUTOFF*CUTOFF*CUTOFF); |
| REF2=2.00*REF1; |
| REF4=2.00*REF2; |
| CUT2=CUTOFF*CUTOFF; /* square of cutoff radius, used |
| to actually decide whether an |
| interaction should be computed in |
| INTERF and POTENG */ |
| |
| FHM=(TSTEP*TSTEP*0.50)/HMAS; |
| FOM=(TSTEP*TSTEP*0.50)/OMAS; |
| NMOL1=NMOL-1; |
| |
| } /* end of subroutine SYSCNS */ |
