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lammps/src/MOLECULE/pair_lj_charmm_coul_charmm_implicit.cpp
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pair_lj_charmm_coul_charmm_implicit.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.
------------------------------------------------------------------------- */
#include <math.h>
#include <string.h>
#include "pair_lj_charmm_coul_charmm_implicit.h"
#include "atom.h"
#include "force.h"
#include "neigh_list.h"
using namespace LAMMPS_NS;
/* ---------------------------------------------------------------------- */
PairLJCharmmCoulCharmmImplicit::PairLJCharmmCoulCharmmImplicit(LAMMPS *lmp) :
PairLJCharmmCoulCharmm(lmp)
{
implicit = 1;
}
/* ---------------------------------------------------------------------- */
void PairLJCharmmCoulCharmmImplicit::compute(int eflag, int vflag)
{
int i,j,ii,jj,inum,jnum,itype,jtype;
double qtmp,xtmp,ytmp,ztmp,delx,dely,delz,evdwl,ecoul,fpair;
double rsq,r2inv,r6inv,forcecoul,forcelj,factor_coul,factor_lj;
double philj,switch1,switch2;
int *ilist,*jlist,*numneigh,**firstneigh;
evdwl = 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;
double *special_lj = force->special_lj;
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_lj = special_lj[sbmask(j)];
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;
if (rsq < cut_bothsq) {
r2inv = 1.0/rsq;
if (rsq < cut_coulsq) {
forcecoul = 2.0 * qqrd2e * qtmp*q[j]*r2inv;
if (rsq > cut_coul_innersq) {
switch1 = (cut_coulsq-rsq) * (cut_coulsq-rsq) *
(cut_coulsq + 2.0*rsq - 3.0*cut_coul_innersq) / denom_coul;
switch2 = 12.0*rsq * (cut_coulsq-rsq) *
(rsq-cut_coul_innersq) / denom_coul;
forcecoul *= switch1 + 0.5*switch2;
}
} else forcecoul = 0.0;
if (rsq < cut_ljsq) {
r6inv = r2inv*r2inv*r2inv;
jtype = type[j];
forcelj = r6inv * (lj1[itype][jtype]*r6inv - lj2[itype][jtype]);
if (rsq > cut_lj_innersq) {
switch1 = (cut_ljsq-rsq) * (cut_ljsq-rsq) *
(cut_ljsq + 2.0*rsq - 3.0*cut_lj_innersq) / denom_lj;
switch2 = 12.0*rsq * (cut_ljsq-rsq) *
(rsq-cut_lj_innersq) / denom_lj;
philj = r6inv * (lj3[itype][jtype]*r6inv - lj4[itype][jtype]);
forcelj = forcelj*switch1 + philj*switch2;
}
} else forcelj = 0.0;
fpair = (factor_coul*forcecoul + factor_lj*forcelj) * 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 (rsq < cut_coulsq) {
ecoul = qqrd2e * qtmp*q[j]*r2inv;
if (rsq > cut_coul_innersq) {
switch1 = (cut_coulsq-rsq) * (cut_coulsq-rsq) *
(cut_coulsq + 2.0*rsq - 3.0*cut_coul_innersq) /
denom_coul;
ecoul *= switch1;
}
ecoul *= factor_coul;
} else ecoul = 0.0;
if (rsq < cut_ljsq) {
evdwl = r6inv*(lj3[itype][jtype]*r6inv-lj4[itype][jtype]);
if (rsq > cut_lj_innersq) {
switch1 = (cut_ljsq-rsq) * (cut_ljsq-rsq) *
(cut_ljsq + 2.0*rsq - 3.0*cut_lj_innersq) / denom_lj;
evdwl *= switch1;
}
evdwl *= factor_lj;
} else evdwl = 0.0;
}
if (evflag) ev_tally(i,j,nlocal,newton_pair,
evdwl,ecoul,fpair,delx,dely,delz);
}
}
}
if (vflag_fdotr) virial_fdotr_compute();
}
/* ---------------------------------------------------------------------- */
double PairLJCharmmCoulCharmmImplicit::single(int i, int j,
int itype, int jtype,
double rsq,
double factor_coul,
double factor_lj,
double &fforce)
{
double r2inv,r6inv,switch1,switch2,forcecoul,forcelj,phicoul,philj;
r2inv = 1.0/rsq;
if (rsq < cut_coulsq) {
forcecoul = 2.0 * force->qqrd2e * atom->q[i]*atom->q[j]*r2inv;
if (rsq > cut_coul_innersq) {
switch1 = (cut_coulsq-rsq) * (cut_coulsq-rsq) *
(cut_coulsq + 2.0*rsq - 3.0*cut_coul_innersq) / denom_coul;
switch2 = 12.0*rsq * (cut_coulsq-rsq) *
(rsq-cut_coul_innersq) / denom_coul;
forcecoul *= switch1 + 0.5*switch2;
}
} else forcecoul = 0.0;
if (rsq < cut_ljsq) {
r6inv = r2inv*r2inv*r2inv;
forcelj = r6inv * (lj1[itype][jtype]*r6inv - lj2[itype][jtype]);
if (rsq > cut_lj_innersq) {
switch1 = (cut_ljsq-rsq) * (cut_ljsq-rsq) *
(cut_ljsq + 2.0*rsq - 3.0*cut_lj_innersq) / denom_lj;
switch2 = 12.0*rsq * (cut_ljsq-rsq) *
(rsq-cut_lj_innersq) / denom_lj;
philj = r6inv * (lj3[itype][jtype]*r6inv - lj4[itype][jtype]);
forcelj = forcelj*switch1 + philj*switch2;
}
} else forcelj = 0.0;
fforce = (factor_coul*forcecoul + factor_lj*forcelj) * r2inv;
double eng = 0.0;
if (rsq < cut_coulsq) {
phicoul = force->qqrd2e * atom->q[i]*atom->q[j]*r2inv;
if (rsq > cut_coul_innersq) {
switch1 = (cut_coulsq-rsq) * (cut_coulsq-rsq) *
(cut_coulsq + 2.0*rsq - 3.0*cut_coul_innersq) /
denom_coul;
phicoul *= switch1;
}
eng += factor_coul*phicoul;
}
if (rsq < cut_ljsq) {
philj = r6inv*(lj3[itype][jtype]*r6inv-lj4[itype][jtype]);
if (rsq > cut_lj_innersq) {
switch1 = (cut_ljsq-rsq) * (cut_ljsq-rsq) *
(cut_ljsq + 2.0*rsq - 3.0*cut_lj_innersq) / denom_lj;
philj *= switch1;
}
eng += factor_lj*philj;
}
return eng;
}
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