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pair_coul_msm.cpp
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Sun, Nov 10, 07:42

pair_coul_msm.cpp
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/* ----------------------------------------------------------------------
LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
http://lammps.sandia.gov, Sandia National Laboratories
Steve Plimpton, sjplimp@sandia.gov
Copyright (2003) Sandia Corporation. Under the terms of Contract
DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
certain rights in this software. This software is distributed under
the GNU General Public License.
See the README file in the top-level LAMMPS directory.
------------------------------------------------------------------------- */
/* ----------------------------------------------------------------------
Contributing authors: Stan Moore (SNL), Paul Crozier (SNL)
------------------------------------------------------------------------- */
#include "math.h"
#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "pair_coul_msm.h"
#include "atom.h"
#include "comm.h"
#include "force.h"
#include "kspace.h"
#include "neighbor.h"
#include "neigh_list.h"
#include "update.h"
#include "integrate.h"
#include "respa.h"
#include "memory.h"
#include "error.h"
using namespace LAMMPS_NS;
/* ---------------------------------------------------------------------- */
PairCoulMSM::PairCoulMSM(LAMMPS *lmp) : PairCoulLong(lmp)
{
ewaldflag = pppmflag = 0;
msmflag = 1;
}
/* ---------------------------------------------------------------------- */
void PairCoulMSM::compute(int eflag, int vflag)
{
int i,j,ii,jj,inum,jnum,itable,itype,jtype;
double qtmp,xtmp,ytmp,ztmp,delx,dely,delz,ecoul,fpair;
double fraction,table;
double r,r2inv,forcecoul,factor_coul;
double egamma,fgamma,prefactor;
int *ilist,*jlist,*numneigh,**firstneigh;
double rsq;
ecoul = 0.0;
if (eflag || vflag) ev_setup(eflag,vflag);
else evflag = vflag_fdotr = 0;
double **x = atom->x;
double **f = atom->f;
double *q = atom->q;
int *type = atom->type;
int nlocal = atom->nlocal;
double *special_coul = force->special_coul;
int newton_pair = force->newton_pair;
double qqrd2e = force->qqrd2e;
inum = list->inum;
ilist = list->ilist;
numneigh = list->numneigh;
firstneigh = list->firstneigh;
// loop over neighbors of my atoms
for (ii = 0; ii < inum; ii++) {
i = ilist[ii];
qtmp = q[i];
xtmp = x[i][0];
ytmp = x[i][1];
ztmp = x[i][2];
itype = type[i];
jlist = firstneigh[i];
jnum = numneigh[i];
for (jj = 0; jj < jnum; jj++) {
j = jlist[jj];
factor_coul = special_coul[sbmask(j)];
j &= NEIGHMASK;
delx = xtmp - x[j][0];
dely = ytmp - x[j][1];
delz = ztmp - x[j][2];
rsq = delx*delx + dely*dely + delz*delz;
jtype = type[j];
if (rsq < cut_coulsq) {
r2inv = 1.0/rsq;
if (!ncoultablebits || rsq <= tabinnersq) {
r = sqrt(rsq);
prefactor = qqrd2e * scale[itype][jtype] * qtmp*q[j]/r;
egamma = 1.0 - (r/cut_coul)*force->kspace->gamma(r/cut_coul);
fgamma = 1.0 + (rsq/cut_coulsq)*force->kspace->dgamma(r/cut_coul);
forcecoul = prefactor * fgamma;
if (factor_coul < 1.0) forcecoul -= (1.0-factor_coul)*prefactor;
} else {
union_int_float_t rsq_lookup;
rsq_lookup.f = rsq;
itable = rsq_lookup.i & ncoulmask;
itable >>= ncoulshiftbits;
fraction = (rsq_lookup.f - rtable[itable]) * drtable[itable];
table = ftable[itable] + fraction*dftable[itable];
forcecoul = scale[itype][jtype] * qtmp*q[j] * table;
if (factor_coul < 1.0) {
table = ctable[itable] + fraction*dctable[itable];
prefactor = scale[itype][jtype] * qtmp*q[j] * table;
forcecoul -= (1.0-factor_coul)*prefactor;
}
}
fpair = forcecoul * r2inv;
f[i][0] += delx*fpair;
f[i][1] += dely*fpair;
f[i][2] += delz*fpair;
if (newton_pair || j < nlocal) {
f[j][0] -= delx*fpair;
f[j][1] -= dely*fpair;
f[j][2] -= delz*fpair;
}
if (eflag) {
if (!ncoultablebits || rsq <= tabinnersq)
ecoul = prefactor*egamma;
else {
table = etable[itable] + fraction*detable[itable];
ecoul = scale[itype][jtype] * qtmp*q[j] * table;
}
if (factor_coul < 1.0) ecoul -= (1.0-factor_coul)*prefactor;
}
if (evflag) ev_tally(i,j,nlocal,newton_pair,
0.0,ecoul,fpair,delx,dely,delz);
}
}
}
if (vflag_fdotr) virial_fdotr_compute();
}
/* ---------------------------------------------------------------------- */
double PairCoulMSM::single(int i, int j, int itype, int jtype,
double rsq,
double factor_coul, double factor_lj,
double &fforce)
{
double r2inv,r,egamma,fgamma,prefactor;
double fraction,table,forcecoul,phicoul;
int itable;
r2inv = 1.0/rsq;
if (!ncoultablebits || rsq <= tabinnersq) {
r = sqrt(rsq);
egamma = 1.0 - (r/cut_coul)*force->kspace->gamma(r/cut_coul);
fgamma = 1.0 + (rsq/cut_coulsq)*force->kspace->dgamma(r/cut_coul);
prefactor = force->qqrd2e * atom->q[i]*atom->q[j]/r;
forcecoul = prefactor * fgamma;
if (factor_coul < 1.0) forcecoul -= (1.0-factor_coul)*prefactor;
} else {
union_int_float_t rsq_lookup;
rsq_lookup.f = rsq;
itable = rsq_lookup.i & ncoulmask;
itable >>= ncoulshiftbits;
fraction = (rsq_lookup.f - rtable[itable]) * drtable[itable];
table = ftable[itable] + fraction*dftable[itable];
forcecoul = atom->q[i]*atom->q[j] * table;
if (factor_coul < 1.0) {
table = ctable[itable] + fraction*dctable[itable];
prefactor = atom->q[i]*atom->q[j] * table;
forcecoul -= (1.0-factor_coul)*prefactor;
}
}
fforce = forcecoul * r2inv;
if (!ncoultablebits || rsq <= tabinnersq)
phicoul = prefactor*egamma;
else {
table = etable[itable] + fraction*detable[itable];
phicoul = atom->q[i]*atom->q[j] * table;
}
if (factor_coul < 1.0) phicoul -= (1.0-factor_coul)*prefactor;
return phicoul;
}
/* ---------------------------------------------------------------------- */
void *PairCoulMSM::extract(const char *str, int &dim)
{
if (strcmp(str,"cut_coul") == 0) {
dim = 0;
return (void *) &cut_coul;
}
if (strcmp(str,"scale") == 0) {
dim = 2;
return (void *) scale;
}
return NULL;
}

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