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lammps/src/USER-MISC/pair_lj_mdf.cpp
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pair_lj_mdf.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 author: Paolo Raiteri (Curtin University)
------------------------------------------------------------------------- */
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "pair_lj_mdf.h"
#include "atom.h"
#include "comm.h"
#include "force.h"
#include "neighbor.h"
#include "neigh_list.h"
#include "memory.h"
#include "error.h"
using namespace LAMMPS_NS;
/* ---------------------------------------------------------------------- */
PairLJMDF::PairLJMDF(LAMMPS *lmp) : Pair(lmp) {}
/* ---------------------------------------------------------------------- */
PairLJMDF::~PairLJMDF()
{
if (allocated) {
memory->destroy(setflag);
memory->destroy(cutsq);
memory->destroy(cut);
memory->destroy(cut_inner);
memory->destroy(cut_inner_sq);
memory->destroy(epsilon);
memory->destroy(sigma);
memory->destroy(lj1);
memory->destroy(lj2);
memory->destroy(lj3);
memory->destroy(lj4);
}
}
/* ---------------------------------------------------------------------- */
void PairLJMDF::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,r2inv,r6inv,forcelj,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;
double *special_lj = force->special_lj;
int newton_pair = force->newton_pair;
double rr, d, dd, tt, dt, dp, philj;
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];
factor_lj = special_lj[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 < cutsq[itype][jtype]) {
r2inv = 1.0/rsq;
r6inv = r2inv*r2inv*r2inv;
forcelj = r6inv * (lj1[itype][jtype]*r6inv - lj2[itype][jtype]);
if (rsq > cut_inner_sq[itype][jtype]) {
philj = r6inv*(lj3[itype][jtype]*r6inv-lj4[itype][jtype]);
rr = sqrt(rsq);
dp = (cut[itype][jtype] - cut_inner[itype][jtype]);
d = (rr-cut_inner[itype][jtype]) / dp;
dd = 1.-d;
// taperig function - mdf style
tt = (1. + 3.*d + 6.*d*d)*dd*dd*dd;
// minus the derivative of the tapering function
dt = 30.* d*d * dd*dd * rr / dp;
forcelj = forcelj*tt + philj*dt;
} else {
tt = 1;
}
fpair = 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) {
evdwl = r6inv * (lj3[itype][jtype]*r6inv - lj4[itype][jtype]);
if (rsq > cut_inner_sq[itype][jtype]) evdwl *= tt;
evdwl *= factor_lj;
if (evflag) ev_tally(i,j,nlocal,newton_pair,
evdwl,0.0,fpair,delx,dely,delz);
}
}
}
}
if (vflag_fdotr) virial_fdotr_compute();
}
/* ----------------------------------------------------------------------
allocate all arrays
------------------------------------------------------------------------- */
void PairLJMDF::allocate()
{
allocated = 1;
int n = atom->ntypes;
memory->create(setflag,n+1,n+1,"pair:setflag");
for (int i = 1; i <= n; i++)
for (int j = i; j <= n; j++)
setflag[i][j] = 0;
memory->create(cutsq,n+1,n+1,"pair:cutsq");
memory->create(cut,n+1,n+1,"pair:cut");
memory->create(cut_inner,n+1,n+1,"pair:cut_inner");
memory->create(cut_inner_sq,n+1,n+1,"pair:cut_inner_sq");
memory->create(epsilon,n+1,n+1,"pair:epsilon");
memory->create(sigma,n+1,n+1,"pair:sigma");
memory->create(lj1,n+1,n+1,"pair:lj1");
memory->create(lj2,n+1,n+1,"pair:lj2");
memory->create(lj3,n+1,n+1,"pair:lj3");
memory->create(lj4,n+1,n+1,"pair:lj4");
}
/* ----------------------------------------------------------------------
global settings
------------------------------------------------------------------------- */
void PairLJMDF::settings(int narg, char **arg)
{
if (narg != 2) error->all(FLERR,"Illegal pair_style command");
cut_inner_global = force->numeric(FLERR,arg[0]);
cut_global = force->numeric(FLERR,arg[1]);
if (cut_inner_global <= 0.0 || cut_inner_global > cut_global)
error->all(FLERR,"Illegal pair_style command");
// 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_inner[i][j] = cut_inner_global;
cut[i][j] = cut_global;
}
}
}
/* ----------------------------------------------------------------------
set coeffs for one or more type pairs
------------------------------------------------------------------------- */
void PairLJMDF::coeff(int narg, char **arg)
{
if (narg != 4 && narg != 6)
error->all(FLERR,"Incorrect args for pair coefficients");
if (!allocated) allocate();
int ilo,ihi,jlo,jhi;
force->bounds(FLERR,arg[0],atom->ntypes,ilo,ihi);
force->bounds(FLERR,arg[1],atom->ntypes,jlo,jhi);
double epsilon_one = force->numeric(FLERR,arg[2]);
double sigma_one = force->numeric(FLERR,arg[3]);
double cut_inner_one = cut_inner_global;
double cut_one = cut_global;
if (narg == 6) {
cut_inner_one = force->numeric(FLERR,arg[4]);
cut_one = force->numeric(FLERR,arg[5]);
}
if (cut_inner_global <= 0.0 || cut_inner_global > cut_global)
error->all(FLERR,"Illegal pair_style command");
int count = 0;
for (int i = ilo; i <= ihi; i++) {
for (int j = MAX(jlo,i); j <= jhi; j++) {
epsilon[i][j] = epsilon_one;
sigma[i][j] = sigma_one;
cut_inner[i][j] = cut_inner_one;
cut[i][j] = cut_one;
setflag[i][j] = 1;
count++;
}
}
if (count == 0) error->all(FLERR,"Incorrect args for pair coefficients");
}
/* ----------------------------------------------------------------------
init for one type pair i,j and corresponding j,i
------------------------------------------------------------------------- */
double PairLJMDF::init_one(int i, int j)
{
if (setflag[i][j] == 0) {
epsilon[i][j] = mix_energy(epsilon[i][i],epsilon[j][j],
sigma[i][i],sigma[j][j]);
sigma[i][j] = mix_distance(sigma[i][i],sigma[j][j]);
cut_inner[i][j] = mix_distance(cut_inner[i][i],cut_inner[j][j]);
cut[i][j] = mix_distance(cut[i][i],cut[j][j]);
}
cut_inner_sq[i][j] = cut_inner[i][j]*cut_inner[i][j];
lj1[i][j] = 48.0 * epsilon[i][j] * pow(sigma[i][j],12.0);
lj2[i][j] = 24.0 * epsilon[i][j] * pow(sigma[i][j],6.0);
lj3[i][j] = 4.0 * epsilon[i][j] * pow(sigma[i][j],12.0);
lj4[i][j] = 4.0 * epsilon[i][j] * pow(sigma[i][j],6.0);
cut[j][i] = cut[i][j]; // BUG FIX
cut_inner[j][i] = cut_inner[i][j];
cut_inner_sq[j][i] = cut_inner_sq[i][j];
lj1[j][i] = lj1[i][j];
lj2[j][i] = lj2[i][j];
lj3[j][i] = lj3[i][j];
lj4[j][i] = lj4[i][j];
return cut[i][j];
}
/* ----------------------------------------------------------------------
proc 0 writes to restart file
------------------------------------------------------------------------- */
void PairLJMDF::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(&epsilon[i][j],sizeof(double),1,fp);
fwrite(&sigma[i][j],sizeof(double),1,fp);
fwrite(&cut_inner[i][j],sizeof(double),1,fp);
fwrite(&cut[i][j],sizeof(double),1,fp);
}
}
}
/* ----------------------------------------------------------------------
proc 0 reads from restart file, bcasts
------------------------------------------------------------------------- */
void PairLJMDF::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(&epsilon[i][j],sizeof(double),1,fp);
fread(&sigma[i][j],sizeof(double),1,fp);
fread(&cut_inner[i][j],sizeof(double),1,fp);
fread(&cut[i][j],sizeof(double),1,fp);
}
MPI_Bcast(&epsilon[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&sigma[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&cut_inner[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&cut[i][j],1,MPI_DOUBLE,0,world);
}
}
}
/* ----------------------------------------------------------------------
proc 0 writes to restart file
------------------------------------------------------------------------- */
void PairLJMDF::write_restart_settings(FILE *fp)
{
fwrite(&mix_flag,sizeof(int),1,fp);
}
/* ----------------------------------------------------------------------
proc 0 reads from restart file, bcasts
------------------------------------------------------------------------- */
void PairLJMDF::read_restart_settings(FILE *fp)
{
int me = comm->me;
if (me == 0) {
fread(&mix_flag,sizeof(int),1,fp);
}
MPI_Bcast(&mix_flag,1,MPI_INT,0,world);
}
/* ---------------------------------------------------------------------- */
double PairLJMDF::single(int i, int j, int itype, int jtype,
double rsq,
double factor_coul, double factor_lj,
double &fforce)
{
double r2inv,r6inv,forcelj,philj;
double rr, dp, d, tt, dt, dd;
r2inv = 1.0/rsq;
r6inv = r2inv*r2inv*r2inv;
philj = r6inv*(lj3[itype][jtype]*r6inv-lj4[itype][jtype]);
forcelj = r6inv * (lj1[itype][jtype]*r6inv - lj2[itype][jtype]);
if (rsq > cut_inner_sq[itype][jtype]) {
rr = sqrt(rsq);
dp = (cut[itype][jtype] - cut_inner[itype][jtype]);
d = (rr - cut_inner[itype][jtype]) / dp;
dd = 1-d;
tt = (1. + 3.*d + 6.*d*d)* dd*dd*dd;
dt = 30.* d*d * dd*dd * rr / dp;
forcelj = forcelj*tt + philj*dt;
philj *= tt;
}
fforce = factor_lj*forcelj*r2inv;
return factor_lj*philj;
}
/* ---------------------------------------------------------------------- */
void *PairLJMDF::extract(const char *str, int &dim)
{
dim = 2;
if (strcmp(str,"epsilon") == 0) return (void *) epsilon;
if (strcmp(str,"sigma") == 0) return (void *) sigma;
return NULL;
}
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