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