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pair_gauss_cut.cpp
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Thu, Jan 23, 06:01

pair_gauss_cut.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: Arben Jusufi, Axel Kohlmeyer (Temple U.)
------------------------------------------------------------------------- */
#include "math.h"
#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "pair_gauss_cut.h"
#include "atom.h"
#include "comm.h"
#include "force.h"
#include "neighbor.h"
#include "neigh_list.h"
#include "update.h"
#include "integrate.h"
#include "memory.h"
#include "error.h"
using namespace LAMMPS_NS;
#define MIN(a,b) ((a) < (b) ? (a) : (b))
#define MAX(a,b) ((a) > (b) ? (a) : (b))
/* ---------------------------------------------------------------------- */
PairGaussCut::PairGaussCut(LAMMPS *lmp) : Pair(lmp)
{
respa_enable = 0;
}
/* ---------------------------------------------------------------------- */
PairGaussCut::~PairGaussCut()
{
if (allocated) {
memory->destroy_2d_int_array(setflag);
memory->destroy_2d_double_array(cutsq);
memory->destroy_2d_double_array(cut);
memory->destroy_2d_double_array(hgauss);
memory->destroy_2d_double_array(sigmah);
memory->destroy_2d_double_array(rmh);
memory->destroy_2d_double_array(pgauss);
memory->destroy_2d_double_array(offset);
}
}
/* ---------------------------------------------------------------------- */
void PairGaussCut::compute(int eflag, int vflag)
{
int i,j,ii,jj,inum,jnum,itype,jtype;
double xtmp,ytmp,ztmp,delx,dely,delz,evdwl,fpair;
double rsq,r,rexp,ugauss,factor_lj;
int *ilist,*jlist,*numneigh,**firstneigh;
evdwl = 0.0;
if (eflag || vflag) ev_setup(eflag,vflag);
else evflag = vflag_fdotr = 0;
double **x = atom->x;
double **f = atom->f;
int *type = atom->type;
int nlocal = atom->nlocal;
int nall = nlocal + atom->nghost;
double *special_lj = force->special_lj;
int newton_pair = force->newton_pair;
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];
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];
if (j < nall) factor_lj = 1.0;
else {
factor_lj = special_lj[j/nall];
j %= nall;
}
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 < cutsq[itype][jtype]) {
r = sqrt(rsq);
rexp = (r-rmh[itype][jtype])/sigmah[itype][jtype];
ugauss = pgauss[itype][jtype]*exp(-0.5*rexp*rexp);
fpair = factor_lj*rexp/r*ugauss/sigmah[itype][jtype];
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) {
evdwl = ugauss - offset[itype][jtype];
evdwl *= factor_lj;
}
if (evflag) ev_tally(i,j,nlocal,newton_pair,
evdwl,0.0,fpair,delx,dely,delz);
}
}
}
if (vflag_fdotr) virial_compute();
}
/* ----------------------------------------------------------------------
allocate all arrays
------------------------------------------------------------------------- */
void PairGaussCut::allocate()
{
allocated = 1;
int n = atom->ntypes;
setflag = memory->create_2d_int_array(n+1,n+1,"pair:setflag");
for (int i = 1; i <= n; i++)
for (int j = i; j <= n; j++)
setflag[i][j] = 0;
cutsq = memory->create_2d_double_array(n+1,n+1,"pair:cutsq");
cut = memory->create_2d_double_array(n+1,n+1,"pair:cut");
hgauss = memory->create_2d_double_array(n+1,n+1,"pair:hgauss");
sigmah = memory->create_2d_double_array(n+1,n+1,"pair:sigmah");
rmh = memory->create_2d_double_array(n+1,n+1,"pair:rmh");
pgauss = memory->create_2d_double_array(n+1,n+1,"pair:pgauss");
offset = memory->create_2d_double_array(n+1,n+1,"pair:offset");
}
/* ----------------------------------------------------------------------
global settings
------------------------------------------------------------------------- */
void PairGaussCut::settings(int narg, char **arg)
{
if (narg != 1) error->all("Illegal pair_style command");
cut_global = force->numeric(arg[0]);
// reset cutoffs that have been explicitly set
if (allocated) {
int i,j;
for (i = 1; i <= atom->ntypes; i++)
for (j = i+1; j <= atom->ntypes; j++)
if (setflag[i][j]) cut[i][j] = cut_global;
}
}
/* ----------------------------------------------------------------------
set coeffs for one or more type pairs
------------------------------------------------------------------------- */
void PairGaussCut::coeff(int narg, char **arg)
{
if (narg < 5 || narg > 6) error->all("Incorrect args for pair coefficients");
if (!allocated) allocate();
int ilo,ihi,jlo,jhi;
force->bounds(arg[0],atom->ntypes,ilo,ihi);
force->bounds(arg[1],atom->ntypes,jlo,jhi);
double hgauss_one = force->numeric(arg[2]);
double rmh_one = force->numeric(arg[3]);
double sigmah_one = force->numeric(arg[4]);
double cut_one = cut_global;
if (narg == 6) cut_one = force->numeric(arg[5]);
int count = 0;
for (int i = ilo; i <= ihi; i++) {
for (int j = MAX(jlo,i); j <= jhi; j++) {
hgauss[i][j] = hgauss_one;
sigmah[i][j] = sigmah_one;
rmh[i][j] = rmh_one;
cut[i][j] = cut_one;
setflag[i][j] = 1;
count++;
}
}
if (count == 0) error->all("Incorrect args for pair coefficients");
}
/* ----------------------------------------------------------------------
init for one type pair i,j and corresponding j,i
------------------------------------------------------------------------- */
double PairGaussCut::init_one(int i, int j)
{
if (setflag[i][j] == 0) {
error->all("for gauss pair style, parameters need to be set explicitly for all pairs.");
}
double PI = 4.0*atan(1.0);
pgauss[i][j] = hgauss[i][j] / sqrt(2.0*PI)/ sigmah[i][j];
if (offset_flag) {
double rexp = (cut[i][j]-rmh[i][j])/sigmah[i][j];
offset[i][j] = pgauss[i][j] * exp(-0.5*rexp*rexp);
} else offset[i][j] = 0.0;
hgauss[j][i] = hgauss[i][j];
sigmah[j][i] = sigmah[i][j];
rmh[j][i] = rmh[i][j];
pgauss[j][i] = pgauss[i][j];
offset[j][i] = offset[i][j];
cut[j][i] = cut[i][j];
// compute I,J contribution to long-range tail correction
// count total # of atoms of type I and J via Allreduce
if (tail_flag) {
int *type = atom->type;
int nlocal = atom->nlocal;
double count[2],all[2];
count[0] = count[1] = 0.0;
for (int k = 0; k < nlocal; k++) {
if (type[k] == i) count[0] += 1.0;
if (type[k] == j) count[1] += 1.0;
}
MPI_Allreduce(count,all,2,MPI_DOUBLE,MPI_SUM,world);
}
return cut[i][j];
}
/* ----------------------------------------------------------------------
proc 0 writes to restart file
------------------------------------------------------------------------- */
void PairGaussCut::write_restart(FILE *fp)
{
write_restart_settings(fp);
int i,j;
for (i = 1; i <= atom->ntypes; i++)
for (j = i; j <= atom->ntypes; j++) {
fwrite(&setflag[i][j],sizeof(int),1,fp);
if (setflag[i][j]) {
fwrite(&hgauss[i][j],sizeof(double),1,fp);
fwrite(&rmh[i][j],sizeof(double),1,fp);
fwrite(&sigmah[i][j],sizeof(double),1,fp);
fwrite(&cut[i][j],sizeof(double),1,fp);
}
}
}
/* ----------------------------------------------------------------------
proc 0 reads from restart file, bcasts
------------------------------------------------------------------------- */
void PairGaussCut::read_restart(FILE *fp)
{
read_restart_settings(fp);
allocate();
int i,j;
int me = comm->me;
for (i = 1; i <= atom->ntypes; i++)
for (j = i; j <= atom->ntypes; j++) {
if (me == 0) fread(&setflag[i][j],sizeof(int),1,fp);
MPI_Bcast(&setflag[i][j],1,MPI_INT,0,world);
if (setflag[i][j]) {
if (me == 0) {
fread(&hgauss[i][j],sizeof(double),1,fp);
fread(&rmh[i][j],sizeof(double),1,fp);
fread(&sigmah[i][j],sizeof(double),1,fp);
fread(&cut[i][j],sizeof(double),1,fp);
}
MPI_Bcast(&hgauss[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&rmh[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&sigmah[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&cut[i][j],1,MPI_DOUBLE,0,world);
}
}
}
/* ----------------------------------------------------------------------
proc 0 writes to restart file
------------------------------------------------------------------------- */
void PairGaussCut::write_restart_settings(FILE *fp)
{
fwrite(&cut_global,sizeof(double),1,fp);
fwrite(&offset_flag,sizeof(int),1,fp);
fwrite(&mix_flag,sizeof(int),1,fp);
}
/* ----------------------------------------------------------------------
proc 0 reads from restart file, bcasts
------------------------------------------------------------------------- */
void PairGaussCut::read_restart_settings(FILE *fp)
{
int me = comm->me;
if (me == 0) {
fread(&cut_global,sizeof(double),1,fp);
fread(&offset_flag,sizeof(int),1,fp);
fread(&mix_flag,sizeof(int),1,fp);
}
MPI_Bcast(&cut_global,1,MPI_DOUBLE,0,world);
MPI_Bcast(&offset_flag,1,MPI_INT,0,world);
MPI_Bcast(&mix_flag,1,MPI_INT,0,world);
}
/* ---------------------------------------------------------------------- */
double PairGaussCut::single(int i, int j, int itype, int jtype, double rsq,
double factor_coul, double factor_lj,
double &fforce)
{
double r, rexp,ugauss,phigauss;
r=sqrt(rsq);
rexp = (r-rmh[itype][jtype])/sigmah[itype][jtype];
ugauss = pgauss[itype][jtype]*exp(-0.5*rexp*rexp);
fforce = factor_lj*rexp/r*ugauss/sigmah[itype][jtype];
phigauss = ugauss - offset[itype][jtype];
return factor_lj*phigauss;
}
/* ---------------------------------------------------------------------- */
double PairGaussCut::memory_usage()
{
const int n=atom->ntypes;
double bytes = Pair::memory_usage();
bytes += 7*((n+1)*(n+1) * sizeof(double) + (n+1)*sizeof(double *));
bytes += 1*((n+1)*(n+1) * sizeof(int) + (n+1)*sizeof(int *));
return bytes;
}

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