git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@7340 f3b2605a-c512-4ea7-a41b-209d697bcdaa
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sjplimp
328
src/pair_coul_wolf.cpp
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328
src/pair_coul_wolf.cpp
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/* ----------------------------------------------------------------------
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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: Yongfeng Zhang (INL), yongfeng.zhang@inl.gov
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------------------------------------------------------------------------- */
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#include "math.h"
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#include "stdio.h"
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#include "stdlib.h"
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#include "string.h"
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#include "pair_coul_wolf.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 "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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PairCoulWolf::PairCoulWolf(LAMMPS *lmp) : Pair(lmp) {}
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/* ---------------------------------------------------------------------- */
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PairCoulWolf::~PairCoulWolf()
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{
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if (allocated) {
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memory->destroy(setflag);
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memory->destroy(cutsq);
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}
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}
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/* ---------------------------------------------------------------------- */
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void PairCoulWolf::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,ecoul,fpair;
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double rsq,forcecoul,factor_coul;
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double prefactor;
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double r,rexp;
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int *ilist,*jlist,*numneigh,**firstneigh;
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double erfcc,erfcd,v_sh,dvdrr,e_self,qisq;
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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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int nall = nlocal + atom->nghost;
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double *special_coul = force->special_coul;
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int newton_pair = force->newton_pair;
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double qqrd2e = force->qqrd2e;
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// self and shifted coulombic energy
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e_self = v_sh = 0.0;
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e_shift = erfc(alf*cut_coul)/cut_coul;
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f_shift = -(e_shift+ 2.0*alf/MY_PIS * exp(-alf*alf*cut_coul*cut_coul)) /
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cut_coul;
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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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qisq = qtmp*qtmp;
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e_self = -(e_shift/2.0 + alf/MY_PIS) * qisq*qqrd2e;
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if (evflag) ev_tally(i,i,nlocal,0,0.0,e_self,0.0,0.0,0.0,0.0);
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for (jj = 0; jj < jnum; jj++) {
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j = jlist[jj];
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if (j < nall) factor_coul = 1.0;
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else {
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factor_coul = special_coul[j/nall];
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j %= nall;
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}
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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 < cut_coulsq) {
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r = sqrt(rsq);
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prefactor = qqrd2e*qtmp*q[j]/r;
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erfcc = erfc(alf*r);
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erfcd = exp(-alf*alf*r*r);
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v_sh = (erfcc - e_shift*r) * prefactor;
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dvdrr = (erfcc/rsq + 2.0*alf/MY_PIS * erfcd/r) + f_shift;
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forcecoul = dvdrr*rsq*prefactor;
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if (factor_coul < 1.0) forcecoul -= (1.0-factor_coul)*prefactor;
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fpair = forcecoul / rsq;
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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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if (eflag) {
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if (rsq < cut_coulsq) {
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ecoul = v_sh;
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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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}
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if (evflag) ev_tally(i,j,nlocal,newton_pair,
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0.0,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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}
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/* ----------------------------------------------------------------------
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allocate all arrays
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------------------------------------------------------------------------- */
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void PairCoulWolf::allocate()
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{
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allocated = 1;
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int n = atom->ntypes;
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memory->create(setflag,n+1,n+1,"pair:setflag");
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for (int i = 1; i <= n; i++)
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for (int j = i; j <= n; j++)
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setflag[i][j] = 0;
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memory->create(cutsq,n+1,n+1,"pair:cutsq");
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}
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/* ----------------------------------------------------------------------
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global settings
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unlike other pair styles,
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there are no individual pair settings that these override
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------------------------------------------------------------------------- */
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void PairCoulWolf::settings(int narg, char **arg)
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{
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if (narg != 2) error->all(FLERR,"Illegal pair_style command");
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alf = force->numeric(arg[0]);
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cut_coul = force->numeric(arg[1]);
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}
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/* ----------------------------------------------------------------------
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set cutoffs for one or more type pairs, optional
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------------------------------------------------------------------------- */
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void PairCoulWolf::coeff(int narg, char **arg)
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{
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if (narg != 2) error->all(FLERR,"Incorrect args for pair coefficients");
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if (!allocated) allocate();
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int ilo,ihi,jlo,jhi;
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force->bounds(arg[0],atom->ntypes,ilo,ihi);
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force->bounds(arg[1],atom->ntypes,jlo,jhi);
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int count = 0;
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for (int i = ilo; i <= ihi; i++) {
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for (int j = MAX(jlo,i); j <= jhi; j++) {
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setflag[i][j] = 1;
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count++;
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}
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}
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if (count == 0) error->all(FLERR,"Incorrect args for pair coefficients");
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}
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/* ----------------------------------------------------------------------
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init specific to this pair style
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------------------------------------------------------------------------- */
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void PairCoulWolf::init_style()
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{
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if (!atom->q_flag)
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error->all(FLERR,"Pair coul/wolf requires atom attribute q");
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int irequest = neighbor->request(this);
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cut_coulsq = cut_coul*cut_coul;
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}
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/* ----------------------------------------------------------------------
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init for one type pair i,j and corresponding j,i
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------------------------------------------------------------------------- */
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double PairCoulWolf::init_one(int i, int j)
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{
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return cut_coul;
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}
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/* ----------------------------------------------------------------------
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proc 0 writes to restart file
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------------------------------------------------------------------------- */
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void PairCoulWolf::write_restart(FILE *fp)
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{
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write_restart_settings(fp);
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int i,j;
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for (i = 1; i <= atom->ntypes; i++)
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for (j = i; j <= atom->ntypes; j++)
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fwrite(&setflag[i][j],sizeof(int),1,fp);
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}
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/* ----------------------------------------------------------------------
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proc 0 reads from restart file, bcasts
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------------------------------------------------------------------------- */
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void PairCoulWolf::read_restart(FILE *fp)
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{
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read_restart_settings(fp);
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allocate();
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int i,j;
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int me = comm->me;
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for (i = 1; i <= atom->ntypes; i++)
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for (j = i; j <= atom->ntypes; j++) {
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if (me == 0) fread(&setflag[i][j],sizeof(int),1,fp);
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MPI_Bcast(&setflag[i][j],1,MPI_INT,0,world);
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}
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}
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/* ----------------------------------------------------------------------
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proc 0 writes to restart file
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------------------------------------------------------------------------- */
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void PairCoulWolf::write_restart_settings(FILE *fp)
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{
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fwrite(&alf,sizeof(double),1,fp);
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fwrite(&cut_coul,sizeof(double),1,fp);
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fwrite(&offset_flag,sizeof(int),1,fp);
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fwrite(&mix_flag,sizeof(int),1,fp);
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}
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/* ----------------------------------------------------------------------
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proc 0 reads from restart file, bcasts
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------------------------------------------------------------------------- */
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void PairCoulWolf::read_restart_settings(FILE *fp)
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{
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if (comm->me == 0) {
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fread(&alf,sizeof(double),1,fp);
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fread(&cut_coul,sizeof(double),1,fp);
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fread(&offset_flag,sizeof(int),1,fp);
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fread(&mix_flag,sizeof(int),1,fp);
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}
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MPI_Bcast(&alf,1,MPI_DOUBLE,0,world);
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MPI_Bcast(&cut_coul,1,MPI_DOUBLE,0,world);
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MPI_Bcast(&offset_flag,1,MPI_INT,0,world);
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MPI_Bcast(&mix_flag,1,MPI_INT,0,world);
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}
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/* ----------------------------------------------------------------------
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only the pair part is calculated here
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------------------------------------------------------------------------- */
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double PairCoulWolf::single(int i, int j, int itype, int jtype, 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 r6inv,r,prefactor,rexp;
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double forcecoul,forceborn,phicoul;
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double e_shift,f_shift,dvdrr,erfcc,erfcd;
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e_shift = erfc(alf*cut_coul) / cut_coul;
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f_shift = -(e_shift+ 2.0*alf/MY_PIS * exp(-alf*alf*cut_coul*cut_coul)) /
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cut_coul;
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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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erfcc = erfc(alf*r);
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erfcd = exp(-alf*alf*r*r);
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dvdrr = (erfcc/rsq + 2.0*alf/MY_PIS * erfcd/r) + f_shift;
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forcecoul = dvdrr*rsq*prefactor;
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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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fforce = forcecoul / rsq;
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double eng = 0.0;
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if (rsq < cut_coulsq) {
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phicoul = prefactor * (erfcc-e_shift*r);
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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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return eng;
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}
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