263 lines
7.9 KiB
C++
263 lines
7.9 KiB
C++
/* ----------------------------------------------------------------------
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LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
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http://lammps.sandia.gov, Sandia National Laboratories
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Steve Plimpton, sjplimp@sandia.gov
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Copyright (2003) Sandia Corporation. Under the terms of Contract
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DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
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certain rights in this software. This software is distributed under
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the GNU General Public License.
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See the README file in the top-level LAMMPS directory.
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------------------------------------------------------------------------- */
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/* ----------------------------------------------------------------------
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Contributing author: Stan Moore (SNL), Paul Crozier (SNL)
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------------------------------------------------------------------------- */
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#include <cmath>
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#include <cstdio>
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#include <cstdlib>
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#include <cstring>
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#include "pair_born_coul_msm.h"
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#include "atom.h"
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#include "comm.h"
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#include "force.h"
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#include "kspace.h"
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#include "neighbor.h"
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#include "neigh_list.h"
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#include "math_const.h"
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#include "memory.h"
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#include "error.h"
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using namespace LAMMPS_NS;
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using namespace MathConst;
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/* ---------------------------------------------------------------------- */
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PairBornCoulMSM::PairBornCoulMSM(LAMMPS *lmp) : PairBornCoulLong(lmp)
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{
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ewaldflag = pppmflag = 0;
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msmflag = 1;
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nmax = 0;
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ftmp = NULL;
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}
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/* ---------------------------------------------------------------------- */
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PairBornCoulMSM::~PairBornCoulMSM()
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{
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if (ftmp) memory->destroy(ftmp);
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}
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/* ---------------------------------------------------------------------- */
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void PairBornCoulMSM::compute(int eflag, int vflag)
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{
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int i,j,ii,jj,inum,jnum,itype,jtype;
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double qtmp,xtmp,ytmp,ztmp,delx,dely,delz,evdwl,ecoul,fpair,fcoul;
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double rsq,r2inv,r6inv,forcecoul,forceborn,factor_coul,factor_lj;
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double egamma,fgamma,prefactor;
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double r,rexp;
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int *ilist,*jlist,*numneigh,**firstneigh;
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int eflag_old = eflag;
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if (force->kspace->scalar_pressure_flag && vflag) {
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if (vflag > 2)
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error->all(FLERR,"Must use 'kspace_modify pressure/scalar no' to "
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"obtain per-atom virial with kspace_style MSM");
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if (atom->nmax > nmax) {
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if (ftmp) memory->destroy(ftmp);
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nmax = atom->nmax;
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memory->create(ftmp,nmax,3,"pair:ftmp");
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}
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memset(&ftmp[0][0],0,nmax*3*sizeof(double));
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// must switch on global energy computation if not already on
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if (eflag == 0 || eflag == 2) {
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eflag++;
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}
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}
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evdwl = ecoul = 0.0;
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if (eflag || vflag) ev_setup(eflag,vflag);
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else evflag = vflag_fdotr = 0;
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double **x = atom->x;
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double **f = atom->f;
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double *q = atom->q;
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int *type = atom->type;
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int nlocal = atom->nlocal;
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double *special_coul = force->special_coul;
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double *special_lj = force->special_lj;
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int newton_pair = force->newton_pair;
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double qqrd2e = force->qqrd2e;
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inum = list->inum;
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ilist = list->ilist;
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numneigh = list->numneigh;
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firstneigh = list->firstneigh;
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// loop over neighbors of my atoms
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for (ii = 0; ii < inum; ii++) {
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i = ilist[ii];
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qtmp = q[i];
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xtmp = x[i][0];
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ytmp = x[i][1];
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ztmp = x[i][2];
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itype = type[i];
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jlist = firstneigh[i];
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jnum = numneigh[i];
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for (jj = 0; jj < jnum; jj++) {
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j = jlist[jj];
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factor_lj = special_lj[sbmask(j)];
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factor_coul = special_coul[sbmask(j)];
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j &= NEIGHMASK;
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delx = xtmp - x[j][0];
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dely = ytmp - x[j][1];
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delz = ztmp - x[j][2];
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rsq = delx*delx + dely*dely + delz*delz;
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jtype = type[j];
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if (rsq < cutsq[itype][jtype]) {
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r2inv = 1.0/rsq;
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r = sqrt(rsq);
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if (rsq < cut_coulsq) {
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prefactor = qqrd2e * qtmp*q[j]/r;
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egamma = 1.0 - (r/cut_coul)*force->kspace->gamma(r/cut_coul);
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fgamma = 1.0 + (rsq/cut_coulsq)*force->kspace->dgamma(r/cut_coul);
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forcecoul = prefactor * fgamma;
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if (factor_coul < 1.0) forcecoul -= (1.0-factor_coul)*prefactor;
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} else forcecoul = 0.0;
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if (rsq < cut_ljsq[itype][jtype]) {
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r6inv = r2inv*r2inv*r2inv;
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rexp = exp((sigma[itype][jtype]-r)*rhoinv[itype][jtype]);
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forceborn = born1[itype][jtype]*r*rexp - born2[itype][jtype]*r6inv
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+ born3[itype][jtype]*r2inv*r6inv;
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} else forceborn = 0.0;
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if (!(force->kspace->scalar_pressure_flag && vflag)) {
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fpair = (forcecoul + factor_lj*forceborn) * r2inv;
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f[i][0] += delx*fpair;
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f[i][1] += dely*fpair;
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f[i][2] += delz*fpair;
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if (newton_pair || j < nlocal) {
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f[j][0] -= delx*fpair;
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f[j][1] -= dely*fpair;
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f[j][2] -= delz*fpair;
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}
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} else {
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// separate Born and Coulombic forces
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fpair = (factor_lj*forceborn) * r2inv;
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f[i][0] += delx*fpair;
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f[i][1] += dely*fpair;
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f[i][2] += delz*fpair;
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if (newton_pair || j < nlocal) {
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f[j][0] -= delx*fpair;
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f[j][1] -= dely*fpair;
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f[j][2] -= delz*fpair;
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}
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fcoul = (forcecoul) * r2inv;
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ftmp[i][0] += delx*fcoul;
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ftmp[i][1] += dely*fcoul;
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ftmp[i][2] += delz*fcoul;
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if (newton_pair || j < nlocal) {
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ftmp[j][0] -= delx*fcoul;
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ftmp[j][1] -= dely*fcoul;
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ftmp[j][2] -= delz*fcoul;
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}
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}
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if (eflag) {
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if (rsq < cut_coulsq) {
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ecoul = prefactor*egamma;
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if (factor_coul < 1.0) ecoul -= (1.0-factor_coul)*prefactor;
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} else ecoul = 0.0;
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if (eflag_old && rsq < cut_ljsq[itype][jtype]) {
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evdwl = a[itype][jtype]*rexp - c[itype][jtype]*r6inv
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+ d[itype][jtype]*r6inv*r2inv - offset[itype][jtype];
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evdwl *= factor_lj;
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} else evdwl = 0.0;
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}
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if (evflag) ev_tally(i,j,nlocal,newton_pair,
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evdwl,ecoul,fpair,delx,dely,delz);
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}
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}
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}
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if (vflag_fdotr) virial_fdotr_compute();
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if (force->kspace->scalar_pressure_flag && vflag) {
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for (i = 0; i < 3; i++) virial[i] += force->pair->eng_coul/3.0;
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for (int i = 0; i < nmax; i++) {
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f[i][0] += ftmp[i][0];
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f[i][1] += ftmp[i][1];
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f[i][2] += ftmp[i][2];
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}
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}
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}
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/* ---------------------------------------------------------------------- */
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double PairBornCoulMSM::single(int i, int j, int itype, int jtype,
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double rsq,
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double factor_coul, double factor_lj,
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double &fforce)
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{
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double r2inv,r6inv,r,rexp,egamma,fgamma,prefactor;
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double forcecoul,forceborn,phicoul,phiborn;
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r2inv = 1.0/rsq;
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if (rsq < cut_coulsq) {
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r = sqrt(rsq);
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prefactor = force->qqrd2e * atom->q[i]*atom->q[j]/r;
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egamma = 1.0 - (r/cut_coul)*force->kspace->gamma(r/cut_coul);
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fgamma = 1.0 + (rsq/cut_coulsq)*force->kspace->dgamma(r/cut_coul);
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forcecoul = prefactor * fgamma;
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if (factor_coul < 1.0) forcecoul -= (1.0-factor_coul)*prefactor;
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} else forcecoul = 0.0;
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if (rsq < cut_ljsq[itype][jtype]) {
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r6inv = r2inv*r2inv*r2inv;
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r = sqrt(rsq);
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rexp = exp((sigma[itype][jtype]-r)*rhoinv[itype][jtype]);
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forceborn = born1[itype][jtype]*r*rexp - born2[itype][jtype]*r6inv +
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born3[itype][jtype]*r2inv*r6inv;
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} else forceborn = 0.0;
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fforce = (forcecoul + factor_lj*forceborn) * r2inv;
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double eng = 0.0;
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if (rsq < cut_coulsq) {
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phicoul = prefactor*egamma;
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if (factor_coul < 1.0) phicoul -= (1.0-factor_coul)*prefactor;
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eng += phicoul;
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}
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if (rsq < cut_ljsq[itype][jtype]) {
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phiborn = a[itype][jtype]*rexp - c[itype][jtype]*r6inv +
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d[itype][jtype]*r2inv*r6inv - offset[itype][jtype];
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eng += factor_lj*phiborn;
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}
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return eng;
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}
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/* ---------------------------------------------------------------------- */
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void *PairBornCoulMSM::extract(const char *str, int &dim)
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{
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dim = 0;
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if (strcmp(str,"cut_coul") == 0) return (void *) &cut_coul;
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return NULL;
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}
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