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lammps/src/SPIN/pair_spin.cpp
julient31 54832a8fe4 Commit Julien 09/14/17 
- Changes and corrections in the computation of the energy
- Issue with newton_pair in the compute of pair
2018-04-26 14:58:41 -06:00

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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: Julien Tranchida (SNL)
Aidan Thompson (SNL)
------------------------------------------------------------------------- */
#include <math.h>
#include <stdlib.h>
#include <string.h>
#include "atom.h"
#include "comm.h"
#include "error.h"
#include "force.h"
#include "neighbor.h"
#include "neigh_list.h"
#include "neigh_request.h"
#include "math_const.h"
#include "memory.h"
#include "pair_spin.h"
#include "update.h"
using namespace LAMMPS_NS;
using namespace MathConst;
/* ---------------------------------------------------------------------- */
PairSpin::PairSpin(LAMMPS *lmp) : Pair(lmp)
{
hbar = force->hplanck/MY_2PI;
newton_pair_spin = 0; // no newton pair for now
single_enable = 0;
exch_flag = 0;
dmi_flag = 0;
me_flag = 0;
no_virial_fdotr_compute = 1;
}
/* ---------------------------------------------------------------------- */
PairSpin::~PairSpin()
{
if (allocated) {
memory->destroy(setflag);
memory->destroy(cut_spin_exchange);
memory->destroy(J1_mag);
memory->destroy(J1_mech);
memory->destroy(J2);
memory->destroy(J3);
memory->destroy(cut_spin_dmi);
memory->destroy(DM);
memory->destroy(v_dmx);
memory->destroy(v_dmy);
memory->destroy(v_dmz);
memory->destroy(cut_spin_me);
memory->destroy(ME);
memory->destroy(v_mex);
memory->destroy(v_mey);
memory->destroy(v_mez);
memory->destroy(spi);
memory->destroy(spj);
memory->destroy(fi);
memory->destroy(fj);
memory->destroy(fmi);
memory->destroy(fmj);
memory->destroy(del);
memory->destroy(cutsq);
}
}
/* ---------------------------------------------------------------------- */
void PairSpin::compute(int eflag, int vflag)
{
int i,j,ii,jj,inum,jnum,itype,jtype;
double evdwl,ecoul;
double xtmp,ytmp,ztmp;
double fix,fiy,fiz,fjx,fjy,fjz;
double fmix,fmiy,fmiz,fmjx,fmjy,fmjz;
double cut_ex_2,cut_dmi_2,cut_me_2,cut_spin_pair_global2;
double rsq,rd;
int *ilist,*jlist,*numneigh,**firstneigh;
evdwl = ecoul = 0.0;
if (eflag || vflag) ev_setup(eflag,vflag);
else evflag = vflag_fdotr = 0;
cut_spin_pair_global2 = cut_spin_pair_global*cut_spin_pair_global;
double **x = atom->x;
double **f = atom->f;
double **fm = atom->fm;
double *mumag = atom->mumag;
double **sp = atom->sp;
int *type = atom->type;
int nlocal = atom->nlocal;
int newton_pair = force->newton_pair;
inum = list->inum;
ilist = list->ilist;
numneigh = list->numneigh;
firstneigh = list->firstneigh;
// pair spin computations
// 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];
jlist = firstneigh[i];
jnum = numneigh[i];
spi[0] = sp[i][0];
spi[1] = sp[i][1];
spi[2] = sp[i][2];
// loop on neighbors
for (jj = 0; jj < jnum; jj++) {
j = jlist[jj];
j &= NEIGHMASK;
spj[0] = sp[j][0];
spj[1] = sp[j][1];
spj[2] = sp[j][2];
fi[0] = fi[1] = fi[2] = 0.0;
fj[0] = fj[1] = fj[2] = 0.0;
fmi[0] = fmi[1] = fmi[2] = 0.0;
fmj[0] = fmj[1] = fmj[2] = 0.0;
del[0] = del[1] = del[2] = 0.0;
del[0] = x[j][0] - xtmp;
del[1] = x[j][1] - ytmp;
del[2] = x[j][2] - ztmp;
// square of inter-atomic distance
rsq = del[0]*del[0] + del[1]*del[1] + del[2]*del[2];
itype = type[i];
jtype = type[j];
// exchange interaction
if (exch_flag) {
cut_ex_2 = cut_spin_exchange[itype][jtype]*cut_spin_exchange[itype][jtype];
if (rsq <= cut_ex_2) {
compute_exchange(i,j,rsq,fmi,fmj,spi,spj);
compute_exchange_mech(i,j,rsq,del,fi,fj,spi,spj);
}
}
// dm interaction
if (dmi_flag){
cut_dmi_2 = cut_spin_dmi[itype][jtype]*cut_spin_dmi[itype][jtype];
if (rsq <= cut_dmi_2){
compute_dmi(i,j,fmi,fmj,spi,spj);
}
}
// me interaction
if (me_flag){
cut_me_2 = cut_spin_me[itype][jtype]*cut_spin_me[itype][jtype];
if (rsq <= cut_me_2){
compute_me(i,j,fmi,fmj,spi,spj);
}
}
f[i][0] += fi[0];
f[i][1] += fi[1];
f[i][2] += fi[2];
fm[i][0] += fmi[0];
fm[i][1] += fmi[1];
fm[i][2] += fmi[2];
/* if (newton_pair || j < nlocal) {*/
if (newton_pair_spin) {
f[j][0] += fj[0];
f[j][1] += fj[1];
f[j][2] += fj[2];
fm[j][0] += fmj[0];
fm[j][1] += fmj[1];
fm[j][2] += fmj[2];
}
if (eflag) {
if (rsq <= cut_spin_pair_global2) {
evdwl -= mumag[i]*spi[0]*fmi[0];
evdwl -= mumag[i]*spi[1]*fmi[1];
evdwl -= mumag[i]*spi[2]*fmi[2];
}
}
evdwl *= hbar;
if (evflag) ev_tally_xyz(i,j,nlocal,newton_pair,
evdwl,ecoul,fi[0],fi[1],fi[2],del[0],del[1],del[2]);
}
}
if (vflag_fdotr) virial_fdotr_compute();
}
/* ---------------------------------------------------------------------- */
void PairSpin::compute_exchange(int i, int j, double rsq, double *fmi, double *fmj, double *spi, double *spj)
{
int *type = atom->type;
int itype, jtype;
double Jex, ra;
itype = type[i];
jtype = type[j];
ra = rsq/J3[itype][jtype]/J3[itype][jtype];
Jex = 4.0*J1_mag[itype][jtype]*ra;
Jex *= (1.0-J2[itype][jtype]*ra);
Jex *= exp(-ra);
fmi[0] += Jex*spj[0];
fmi[1] += Jex*spj[1];
fmi[2] += Jex*spj[2];
fmj[0] += Jex*spi[0];
fmj[1] += Jex*spi[1];
fmj[2] += Jex*spi[2];
}
/* ---------------------------------------------------------------------- */
void PairSpin::compute_exchange_mech(int i, int j, double rsq, double *del, double *fi, double *fj, double *spi, double *spj)
{
int *type = atom->type;
int itype, jtype;
double Jex, Jex_mech, ra, rr;
itype = type[i];
jtype = type[j];
Jex = J1_mech[itype][jtype];
ra = rsq/J3[itype][jtype]/J3[itype][jtype];
rr = sqrt(rsq)/J3[itype][jtype]/J3[itype][jtype];
Jex_mech = 1.0-ra-J2[itype][jtype]*ra*(2.0-ra);
Jex_mech *= 8.0*Jex*rr*exp(-ra);
Jex_mech *= (spi[0]*spj[0]+spi[1]*spj[1]+spi[2]*spj[2]);
fi[0] += Jex_mech*del[0];
fi[1] += Jex_mech*del[1];
fi[2] += Jex_mech*del[2];
fj[0] -= Jex_mech*del[0];
fj[1] -= Jex_mech*del[1];
fj[2] -= Jex_mech*del[2];
}
/* ---------------------------------------------------------------------- */
void PairSpin::compute_dmi(int i, int j, double *fmi, double *fmj, double *spi, double *spj)
{
int *type = atom->type;
int itype, jtype;
double dmix,dmiy,dmiz;
itype = type[i];
jtype = type[j];
dmix = DM[itype][jtype]*v_dmx[itype][jtype];
dmiy = DM[itype][jtype]*v_dmy[itype][jtype];
dmiz = DM[itype][jtype]*v_dmz[itype][jtype];
fmi[0] += spj[1]*dmiz-spj[2]*dmiy;
fmi[1] += spj[2]*dmix-spj[0]*dmiz;
fmi[2] += spj[0]*dmiy-spj[1]*dmix;
fmj[0] -= spi[1]*dmiz-spi[2]*dmiy;
fmj[1] -= spi[2]*dmix-spi[0]*dmiz;
fmj[2] -= spi[0]*dmiy-spi[1]*dmix;
}
/* ---------------------------------------------------------------------- */
void PairSpin::compute_me(int i, int j, double *fmi, double *fmj, double *spi, double *spj)
{
int *type = atom->type;
int itype, jtype;
itype = type[i];
jtype = type[j];
double **sp = atom->sp;
double **x = atom->x;
double meix,meiy,meiz;
double rx, ry, rz, inorm;
rx = x[j][0] - x[i][0];
ry = x[j][1] - x[i][1];
rz = x[j][2] - x[i][2];
inorm = 1.0/sqrt(rx*rx+ry*ry+rz*rz);
rx *= inorm;
ry *= inorm;
rz *= inorm;
meix = v_mey[itype][jtype]*rz - v_mez[itype][jtype]*ry;
meiy = v_mez[itype][jtype]*rx - v_mex[itype][jtype]*rz;
meiz = v_mex[itype][jtype]*ry - v_mey[itype][jtype]*rx;
meix *= ME[itype][jtype];
meiy *= ME[itype][jtype];
meiz *= ME[itype][jtype];
fmi[0] += spj[1]*meiz - spj[2]*meiy;
fmi[1] += spj[2]*meix - spj[0]*meiz;
fmi[2] += spj[0]*meiy - spj[1]*meix;
fmj[0] -= spi[1]*meiz - spi[2]*meiy;
fmj[1] -= spi[2]*meix - spi[0]*meiz;
fmj[2] -= spi[0]*meiy - spi[1]*meix;
}
/* ----------------------------------------------------------------------
allocate all arrays
------------------------------------------------------------------------- */
void PairSpin::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(cut_spin_exchange,n+1,n+1,"pair:cut_spin_exchange");
memory->create(J1_mag,n+1,n+1,"pair:J1_mag");
memory->create(J1_mech,n+1,n+1,"pair:J1_mech");
memory->create(J2,n+1,n+1,"pair:J2");
memory->create(J3,n+1,n+1,"pair:J3");
memory->create(cut_spin_dmi,n+1,n+1,"pair:cut_spin_dmi");
memory->create(DM,n+1,n+1,"pair:DM");
memory->create(v_dmx,n+1,n+1,"pair:DM_vector_x");
memory->create(v_dmy,n+1,n+1,"pair:DM_vector_y");
memory->create(v_dmz,n+1,n+1,"pair:DM_vector_z");
memory->create(cut_spin_me,n+1,n+1,"pair:cut_spin_me");
memory->create(ME,n+1,n+1,"pair:ME");
memory->create(v_mex,n+1,n+1,"pair:ME_vector_x");
memory->create(v_mey,n+1,n+1,"pair:ME_vector_y");
memory->create(v_mez,n+1,n+1,"pair:ME_vector_z");
memory->create(spi,3,"pair:spi");
memory->create(spj,3,"pair:spj");
memory->create(fi,3,"pair:fi");
memory->create(fj,3,"pair:fj");
memory->create(fmi,3,"pair:fmi");
memory->create(fmj,3,"pair:fmj");
memory->create(del,3,"pair:del");
memory->create(cutsq,n+1,n+1,"pair:cutsq");
}
/* ----------------------------------------------------------------------
global settings
------------------------------------------------------------------------- */
void PairSpin::settings(int narg, char **arg)
{
if (narg < 1 || narg > 2)
error->all(FLERR,"Incorrect number of args in pair_style pair/spin command");
if (strcmp(update->unit_style,"metal") != 0)
error->all(FLERR,"Spin simulations require metal unit style");
cut_spin_pair_global = force->numeric(FLERR,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_spin_exchange[i][j] = cut_spin_pair_global;
cut_spin_dmi[i][j] = cut_spin_pair_global;
cut_spin_me[i][j] = cut_spin_pair_global;
}
}
}
/* ----------------------------------------------------------------------
set coeffs for one or more type spin pairs (only one for now)
------------------------------------------------------------------------- */
void PairSpin::coeff(int narg, char **arg)
{
const double hbar = force->hplanck/MY_2PI;
if (!allocated) allocate();
if (strcmp(arg[2],"exchange")==0){
if (narg != 7) error->all(FLERR,"Incorrect args in pair_style command");
exch_flag = 1;
int ilo,ihi,jlo,jhi;
force->bounds(FLERR,arg[0],atom->ntypes,ilo,ihi);
force->bounds(FLERR,arg[1],atom->ntypes,jlo,jhi);
const double rij = force->numeric(FLERR,arg[3]);
const double j1 = (force->numeric(FLERR,arg[4]));
const double j2 = force->numeric(FLERR,arg[5]);
const double j3 = force->numeric(FLERR,arg[6]);
int count = 0;
for (int i = ilo; i <= ihi; i++) {
for (int j = MAX(jlo,i); j <= jhi; j++) {
cut_spin_exchange[i][j] = rij;
J1_mag[i][j] = j1/hbar;
J1_mech[i][j] = j1;
J2[i][j] = j2;
J3[i][j] = j3;
setflag[i][j] = 1;
count++;
}
}
if (count == 0) error->all(FLERR,"Incorrect args in pair_style command");
} else if (strcmp(arg[2],"dmi")==0) {
if (narg != 8) error->all(FLERR,"Incorrect args in pair_style command");
dmi_flag = 1;
int ilo,ihi,jlo,jhi;
force->bounds(FLERR,arg[0],atom->ntypes,ilo,ihi);
force->bounds(FLERR,arg[1],atom->ntypes,jlo,jhi);
const double rij = force->numeric(FLERR,arg[3]);
const double dm = (force->numeric(FLERR,arg[4]))/hbar;
double dmx = force->numeric(FLERR,arg[5]);
double dmy = force->numeric(FLERR,arg[6]);
double dmz = force->numeric(FLERR,arg[7]);
double inorm = 1.0/(dmx*dmx+dmy*dmy+dmz*dmz);
dmx *= inorm;
dmy *= inorm;
dmz *= inorm;
int count = 0;
for (int i = ilo; i <= ihi; i++) {
for (int j = MAX(jlo,i); j <= jhi; j++) {
cut_spin_dmi[i][j] = rij;
DM[i][j] = dm;
v_dmx[i][j] = dmx;
v_dmy[i][j] = dmy;
v_dmz[i][j] = dmz;
setflag[i][j] = 1;
count++;
}
}
if (count == 0) error->all(FLERR,"Incorrect args in pair_style command");
} else if (strcmp(arg[2],"me")==0) {
if (narg != 8) error->all(FLERR,"Incorrect args in pair_style command");
me_flag = 1;
int ilo,ihi,jlo,jhi;
force->bounds(FLERR,arg[0],atom->ntypes,ilo,ihi);
force->bounds(FLERR,arg[1],atom->ntypes,jlo,jhi);
const double rij = force->numeric(FLERR,arg[3]);
const double me = (force->numeric(FLERR,arg[4]))/hbar;
double mex = force->numeric(FLERR,arg[5]);
double mey = force->numeric(FLERR,arg[6]);
double mez = force->numeric(FLERR,arg[7]);
double inorm = 1.0/(mex*mex+mey*mey+mez*mez);
mex *= inorm;
mey *= inorm;
mez *= inorm;
int count = 0;
for (int i = ilo; i <= ihi; i++) {
for (int j = MAX(jlo,i); j <= jhi; j++) {
cut_spin_me[i][j] = rij;
DM[i][j] = me;
v_mex[i][j] = mex;
v_mey[i][j] = mey;
v_mez[i][j] = mez;
setflag[i][j] = 1;
count++;
}
}
if (count == 0) error->all(FLERR,"Incorrect args in pair_style command");
} else error->all(FLERR,"Incorrect args in pair_style command");
// check if Jex [][] still works for Ferrimagnetic exchange
}
/* ----------------------------------------------------------------------
init specific to this pair style
------------------------------------------------------------------------- */
void PairSpin::init_style()
{
if (!atom->sp_flag || !atom->mumag_flag)
error->all(FLERR,"Pair spin requires atom attributes sp, mumag");
neighbor->request(this,instance_me);
#define FULLNEI
#if defined FULLNEI
int irequest = neighbor->request(this,instance_me);
neighbor->requests[irequest]->half = 0;
neighbor->requests[irequest]->full = 1;
#endif
}
/* ----------------------------------------------------------------------
init for one type pair i,j and corresponding j,i
------------------------------------------------------------------------- */
double PairSpin::init_one(int i, int j)
{
if (setflag[i][j] == 0) error->all(FLERR,"All pair coeffs are not set");
return cut_spin_pair_global;
}
/* ----------------------------------------------------------------------
proc 0 writes to restart file
------------------------------------------------------------------------- */
void PairSpin::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]) {
if (exch_flag){
fwrite(&J1_mag[i][j],sizeof(double),1,fp);
fwrite(&J1_mech[i][j],sizeof(double),1,fp);
fwrite(&J2[i][j],sizeof(double),1,fp);
fwrite(&J3[i][j],sizeof(double),1,fp);
fwrite(&cut_spin_exchange[i][j],sizeof(double),1,fp);
}
if (dmi_flag) {
fwrite(&DM[i][j],sizeof(double),1,fp);
fwrite(&v_dmx[i][j],sizeof(double),1,fp);
fwrite(&v_dmy[i][j],sizeof(double),1,fp);
fwrite(&v_dmz[i][j],sizeof(double),1,fp);
fwrite(&cut_spin_dmi[i][j],sizeof(double),1,fp);
}
if (me_flag) {
fwrite(&ME[i][j],sizeof(double),1,fp);
fwrite(&v_mex[i][j],sizeof(double),1,fp);
fwrite(&v_mey[i][j],sizeof(double),1,fp);
fwrite(&v_mez[i][j],sizeof(double),1,fp);
fwrite(&cut_spin_me[i][j],sizeof(double),1,fp);
}
}
}
}
/* ----------------------------------------------------------------------
proc 0 reads from restart file, bcasts
------------------------------------------------------------------------- */
void PairSpin::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(&J1_mag[i][j],sizeof(double),1,fp);
fread(&J1_mech[i][j],sizeof(double),1,fp);
fread(&J2[i][j],sizeof(double),1,fp);
fread(&J2[i][j],sizeof(double),1,fp);
fread(&cut_spin_exchange[i][j],sizeof(double),1,fp);
}
MPI_Bcast(&J1_mag[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&J1_mech[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&J2[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&J3[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&cut_spin_exchange[i][j],1,MPI_DOUBLE,0,world);
}
}
}
}
/* ----------------------------------------------------------------------
proc 0 writes to restart file
------------------------------------------------------------------------- */
void PairSpin::write_restart_settings(FILE *fp)
{
fwrite(&cut_spin_pair_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 PairSpin::read_restart_settings(FILE *fp)
{
if (comm->me == 0) {
fread(&cut_spin_pair_global,sizeof(double),1,fp);
fread(&offset_flag,sizeof(int),1,fp);
fread(&mix_flag,sizeof(int),1,fp);
}
MPI_Bcast(&cut_spin_pair_global,1,MPI_DOUBLE,0,world);
MPI_Bcast(&offset_flag,1,MPI_INT,0,world);
MPI_Bcast(&mix_flag,1,MPI_INT,0,world);
}
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