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lammps/src/SPIN/pair_spin_exchange_biquadratic.cpp
Axel Kohlmeyer 2132b1d904 update developer reference text
2022-10-24 11:08:26 -04:00

628 lines
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// clang-format off
/* ----------------------------------------------------------------------
LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
https://www.lammps.org/, Sandia National Laboratories
LAMMPS development team: developers@lammps.org
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)
Please cite the related publication:
Tranchida, J., Plimpton, S. J., Thibaudeau, P., & Thompson, A. P. (2018).
Massively parallel symplectic algorithm for coupled magnetic spin dynamics
and molecular dynamics. Journal of Computational Physics.
------------------------------------------------------------------------- */
#include "pair_spin_exchange_biquadratic.h"
#include "atom.h"
#include "comm.h"
#include "error.h"
#include "force.h"
#include "memory.h"
#include "neigh_list.h"
#include <cmath>
#include <cstring>
using namespace LAMMPS_NS;
/* ---------------------------------------------------------------------- */
PairSpinExchangeBiquadratic::PairSpinExchangeBiquadratic(LAMMPS *lmp) :
PairSpin(lmp)
{
e_offset = 0;
}
/* ---------------------------------------------------------------------- */
PairSpinExchangeBiquadratic::~PairSpinExchangeBiquadratic()
{
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(K1_mag);
memory->destroy(K1_mech);
memory->destroy(K2);
memory->destroy(K3);
memory->destroy(cutsq); // to be implemented
memory->destroy(emag);
}
}
/* ----------------------------------------------------------------------
global settings
------------------------------------------------------------------------- */
void PairSpinExchangeBiquadratic::settings(int narg, char **arg)
{
PairSpin::settings(narg,arg);
if (narg != 1) error->all(FLERR,"Illegal pair_style command");
cut_spin_exchange_global = utils::numeric(FLERR,arg[0],false,lmp);
// 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_exchange_global;
}
}
}
/* ----------------------------------------------------------------------
set coeffs for one or more type spin pairs
------------------------------------------------------------------------- */
void PairSpinExchangeBiquadratic::coeff(int narg, char **arg)
{
if (!allocated) allocate();
// check if args correct
if (strcmp(arg[2],"biquadratic") != 0)
error->all(FLERR,"Incorrect args for pair coefficients");
if ((narg != 10) && (narg != 12))
error->all(FLERR,"Incorrect args for pair coefficients");
int ilo,ihi,jlo,jhi;
utils::bounds(FLERR,arg[0],1,atom->ntypes,ilo,ihi,error);
utils::bounds(FLERR,arg[1],1,atom->ntypes,jlo,jhi,error);
// get exchange arguments from input command
int iarg = 10;
const double rc = utils::numeric(FLERR,arg[3],false,lmp);
const double j1 = utils::numeric(FLERR,arg[4],false,lmp);
const double j2 = utils::numeric(FLERR,arg[5],false,lmp);
const double j3 = utils::numeric(FLERR,arg[6],false,lmp);
const double k1 = utils::numeric(FLERR,arg[7],false,lmp);
const double k2 = utils::numeric(FLERR,arg[8],false,lmp);
const double k3 = utils::numeric(FLERR,arg[9],false,lmp);
// read energy offset flag if specified
while (iarg < narg) {
if (strcmp(arg[iarg],"offset") == 0) {
e_offset = utils::logical(FLERR,arg[iarg+1],false,lmp);
iarg += 2;
} else error->all(FLERR,"Incorrect args for pair coefficients");
}
int count = 0;
for (int i = ilo; i <= ihi; i++) {
for (int j = MAX(jlo,i); j <= jhi; j++) {
cut_spin_exchange[i][j] = rc;
J1_mag[i][j] = j1/hbar;
J1_mech[i][j] = j1;
J2[i][j] = j2;
J3[i][j] = j3;
K1_mag[i][j] = k1/hbar;
K1_mech[i][j] = k1;
K2[i][j] = k2;
K3[i][j] = k3;
setflag[i][j] = 1;
count++;
}
}
if (count == 0) error->all(FLERR,"Incorrect args in pair_style command");
}
/* ----------------------------------------------------------------------
init for one type pair i,j and corresponding j,i
------------------------------------------------------------------------- */
double PairSpinExchangeBiquadratic::init_one(int i, int j)
{
if (setflag[i][j] == 0) error->all(FLERR,"All pair coeffs are not set");
J1_mag[j][i] = J1_mag[i][j];
J1_mech[j][i] = J1_mech[i][j];
J2[j][i] = J2[i][j];
J3[j][i] = J3[i][j];
K1_mag[j][i] = K1_mag[i][j];
K1_mech[j][i] = K1_mech[i][j];
K2[j][i] = K2[i][j];
K3[j][i] = K3[i][j];
cut_spin_exchange[j][i] = cut_spin_exchange[i][j];
return cut_spin_exchange_global;
}
/* ----------------------------------------------------------------------
extract the larger cutoff
------------------------------------------------------------------------- */
void *PairSpinExchangeBiquadratic::extract(const char *str, int &dim)
{
dim = 0;
if (strcmp(str,"cut") == 0) return (void *) &cut_spin_exchange_global;
return nullptr;
}
/* ---------------------------------------------------------------------- */
void PairSpinExchangeBiquadratic::compute(int eflag, int vflag)
{
int i,j,ii,jj,inum,jnum,itype,jtype;
double evdwl, ecoul;
double xi[3], eij[3];
double delx,dely,delz;
double spi[3], spj[3];
double fi[3], fmi[3];
double local_cut2;
double rsq, inorm;
int *ilist,*jlist,*numneigh,**firstneigh;
evdwl = ecoul = 0.0;
ev_init(eflag,vflag);
double **x = atom->x;
double **f = atom->f;
double **fm = atom->fm;
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;
// checking size of emag
if (nlocal_max < nlocal) { // grow emag lists if necessary
nlocal_max = nlocal;
memory->grow(emag,nlocal_max,"pair/spin:emag");
}
// computation of the exchange interaction
// loop over atoms and their neighbors
for (ii = 0; ii < inum; ii++) {
i = ilist[ii];
itype = type[i];
jlist = firstneigh[i];
jnum = numneigh[i];
xi[0] = x[i][0];
xi[1] = x[i][1];
xi[2] = x[i][2];
spi[0] = sp[i][0];
spi[1] = sp[i][1];
spi[2] = sp[i][2];
emag[i] = 0.0;
// loop on neighbors
for (jj = 0; jj < jnum; jj++) {
j = jlist[jj];
j &= NEIGHMASK;
jtype = type[j];
spj[0] = sp[j][0];
spj[1] = sp[j][1];
spj[2] = sp[j][2];
evdwl = 0.0;
fi[0] = fi[1] = fi[2] = 0.0;
fmi[0] = fmi[1] = fmi[2] = 0.0;
delx = xi[0] - x[j][0];
dely = xi[1] - x[j][1];
delz = xi[2] - x[j][2];
rsq = delx*delx + dely*dely + delz*delz;
inorm = 1.0/sqrt(rsq);
eij[0] = -inorm*delx;
eij[1] = -inorm*dely;
eij[2] = -inorm*delz;
local_cut2 = cut_spin_exchange[itype][jtype]*cut_spin_exchange[itype][jtype];
// compute exchange interaction
if (rsq <= local_cut2) {
compute_exchange(i,j,rsq,fmi,spi,spj);
if (lattice_flag)
compute_exchange_mech(i,j,rsq,eij,fi,spi,spj);
if (eflag) {
evdwl -= compute_energy(i,j,rsq,spi,spj);
emag[i] += evdwl;
} else evdwl = 0.0;
f[i][0] += fi[0];
f[i][1] += fi[1];
f[i][2] += fi[2];
if (newton_pair || j < nlocal) {
f[j][0] -= fi[0];
f[j][1] -= fi[1];
f[j][2] -= fi[2];
}
fm[i][0] += fmi[0];
fm[i][1] += fmi[1];
fm[i][2] += fmi[2];
if (evflag) ev_tally_xyz(i,j,nlocal,newton_pair,
evdwl,ecoul,fi[0],fi[1],fi[2],delx,dely,delz);
}
}
}
if (vflag_fdotr) virial_fdotr_compute();
}
/* ----------------------------------------------------------------------
update the pair interactions fmi acting on the spin ii
------------------------------------------------------------------------- */
void PairSpinExchangeBiquadratic::compute_single_pair(int ii, double fmi[3])
{
int *type = atom->type;
double **x = atom->x;
double **sp = atom->sp;
double local_cut2;
double xi[3];
double delx,dely,delz;
double spi[3],spj[3];
int j,jnum,itype,jtype,ntypes;
int k,locflag;
int *jlist,*numneigh,**firstneigh;
double rsq;
numneigh = list->numneigh;
firstneigh = list->firstneigh;
// check if interaction applies to type of ii
itype = type[ii];
ntypes = atom->ntypes;
locflag = 0;
k = 1;
while (k <= ntypes) {
if (k <= itype) {
if (setflag[k][itype] == 1) {
locflag =1;
break;
}
k++;
} else if (k > itype) {
if (setflag[itype][k] == 1) {
locflag =1;
break;
}
k++;
} else error->all(FLERR,"Wrong type number");
}
// if interaction applies to type ii,
// locflag = 1 and compute pair interaction
if (locflag == 1) {
xi[0] = x[ii][0];
xi[1] = x[ii][1];
xi[2] = x[ii][2];
spi[0] = sp[ii][0];
spi[1] = sp[ii][1];
spi[2] = sp[ii][2];
jlist = firstneigh[ii];
jnum = numneigh[ii];
for (int jj = 0; jj < jnum; jj++) {
j = jlist[jj];
j &= NEIGHMASK;
jtype = type[j];
local_cut2 = cut_spin_exchange[itype][jtype]*cut_spin_exchange[itype][jtype];
spj[0] = sp[j][0];
spj[1] = sp[j][1];
spj[2] = sp[j][2];
delx = xi[0] - x[j][0];
dely = xi[1] - x[j][1];
delz = xi[2] - x[j][2];
rsq = delx*delx + dely*dely + delz*delz;
if (rsq <= local_cut2) {
compute_exchange(ii,j,rsq,fmi,spi,spj);
}
}
}
}
/* ----------------------------------------------------------------------
compute exchange interaction between spins i and j
------------------------------------------------------------------------- */
void PairSpinExchangeBiquadratic::compute_exchange(int i, int j, double rsq,
double fmi[3], double spi[3], double spj[3])
{
int *type = atom->type;
int itype,jtype;
double Jex,Kex,r2j,r2k,sdots;
itype = type[i];
jtype = type[j];
r2j = rsq/J3[itype][jtype]/J3[itype][jtype];
r2k = rsq/K3[itype][jtype]/K3[itype][jtype];
Jex = 4.0*J1_mag[itype][jtype]*r2j;
Jex *= (1.0-J2[itype][jtype]*r2j);
Jex *= exp(-r2j);
Kex = 4.0*K1_mag[itype][jtype]*r2k;
Kex *= (1.0-K2[itype][jtype]*r2k);
Kex *= exp(-r2k);
sdots = (spi[0]*spj[0]+spi[1]*spj[1]+spi[2]*spj[2]);
fmi[0] += (Jex*spj[0] + 2.0*Kex*spj[0]*sdots);
fmi[1] += (Jex*spj[1] + 2.0*Kex*spj[1]*sdots);
fmi[2] += (Jex*spj[2] + 2.0*Kex*spj[2]*sdots);
}
/* ----------------------------------------------------------------------
compute the mechanical force due to the exchange interaction between atom i and atom j
------------------------------------------------------------------------- */
void PairSpinExchangeBiquadratic::compute_exchange_mech(int i, int j,
double rsq, double eij[3], double fi[3], double spi[3], double spj[3])
{
int *type = atom->type;
int itype,jtype;
double Jex,Jex_mech,Kex,Kex_mech,sdots;
double rja,rka,rjr,rkr,iJ3,iK3;
double fx, fy, fz;
itype = type[i];
jtype = type[j];
Jex = J1_mech[itype][jtype];
iJ3 = 1.0/(J3[itype][jtype]*J3[itype][jtype]);
Kex = K1_mech[itype][jtype];
iK3 = 1.0/(K3[itype][jtype]*K3[itype][jtype]);
rja = rsq*iJ3;
rjr = sqrt(rsq)*iJ3;
rka = rsq*iK3;
rkr = sqrt(rsq)*iK3;
Jex_mech = 1.0-rja-J2[itype][jtype]*rja*(2.0-rja);
Jex_mech *= 8.0*Jex*rjr*exp(-rja);
Kex_mech = 1.0-rka-K2[itype][jtype]*rka*(2.0-rka);
Kex_mech *= 8.0*Kex*rkr*exp(-rka);
sdots = (spi[0]*spj[0]+spi[1]*spj[1]+spi[2]*spj[2]);
// apply or not energy and force offset
fx = fy = fz = 0.0;
if (e_offset == 1) { // set offset
fx = (Jex_mech*(sdots-1.0) + Kex_mech*(sdots*sdots-1.0))*eij[0];
fy = (Jex_mech*(sdots-1.0) + Kex_mech*(sdots*sdots-1.0))*eij[1];
fz = (Jex_mech*(sdots-1.0) + Kex_mech*(sdots*sdots-1.0))*eij[2];
} else if (e_offset == 0) { // no offset ("normal" calculation)
fx = (Jex_mech*sdots + Kex_mech*sdots*sdots)*eij[0];
fy = (Jex_mech*sdots + Kex_mech*sdots*sdots)*eij[1];
fz = (Jex_mech*sdots + Kex_mech*sdots*sdots)*eij[2];
} else error->all(FLERR,"Illegal option in pair exchange/biquadratic command");
fi[0] -= 0.5*fx;
fi[1] -= 0.5*fy;
fi[2] -= 0.5*fz;
// fi[0] -= fx;
// fi[1] -= fy;
// fi[2] -= fz;
}
/* ----------------------------------------------------------------------
compute energy of spin pair i and j
------------------------------------------------------------------------- */
double PairSpinExchangeBiquadratic::compute_energy(int i, int j, double rsq,
double spi[3], double spj[3])
{
int *type = atom->type;
int itype,jtype;
double Jex,Kex,sdots;
double r2j,r2k;
double energy = 0.0;
itype = type[i];
jtype = type[j];
r2j = rsq/J3[itype][jtype]/J3[itype][jtype];
r2k = rsq/K3[itype][jtype]/K3[itype][jtype];
Jex = 4.0*J1_mech[itype][jtype]*r2j;
Jex *= (1.0-J2[itype][jtype]*r2j);
Jex *= exp(-r2j);
Kex = 4.0*K1_mech[itype][jtype]*r2k;
Kex *= (1.0-K2[itype][jtype]*r2k);
Kex *= exp(-r2k);
sdots = (spi[0]*spj[0]+spi[1]*spj[1]+spi[2]*spj[2]);
// apply or not energy and force offset
if (e_offset == 1) { // set offset
energy = 0.5*(Jex*(sdots-1.0) + Kex*(sdots*sdots-1.0));
} else if (e_offset == 0) { // no offset ("normal" calculation)
energy = 0.5*(Jex*sdots + Kex*sdots*sdots);
} else error->all(FLERR,"Illegal option in pair exchange/biquadratic command");
return energy;
}
/* ----------------------------------------------------------------------
allocate all arrays
------------------------------------------------------------------------- */
void PairSpinExchangeBiquadratic::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/spin/exchange:cut_spin_exchange");
memory->create(J1_mag,n+1,n+1,"pair/spin/exchange:J1_mag");
memory->create(J1_mech,n+1,n+1,"pair/spin/exchange:J1_mech");
memory->create(J2,n+1,n+1,"pair/spin/exchange:J2");
memory->create(J3,n+1,n+1,"pair/spin/exchange:J3");
memory->create(K1_mag,n+1,n+1,"pair/spin/exchange:J1_mag");
memory->create(K1_mech,n+1,n+1,"pair/spin/exchange:J1_mech");
memory->create(K2,n+1,n+1,"pair/spin/exchange:J2");
memory->create(K3,n+1,n+1,"pair/spin/exchange:J3");
memory->create(cutsq,n+1,n+1,"pair:cutsq");
}
/* ----------------------------------------------------------------------
proc 0 writes to restart file
------------------------------------------------------------------------- */
void PairSpinExchangeBiquadratic::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(&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(&K1_mag[i][j],sizeof(double),1,fp);
fwrite(&K1_mech[i][j],sizeof(double),1,fp);
fwrite(&K2[i][j],sizeof(double),1,fp);
fwrite(&K3[i][j],sizeof(double),1,fp);
fwrite(&cut_spin_exchange[i][j],sizeof(double),1,fp);
}
}
}
}
/* ----------------------------------------------------------------------
proc 0 reads from restart file, bcasts
------------------------------------------------------------------------- */
void PairSpinExchangeBiquadratic::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) utils::sfread(FLERR,&setflag[i][j],sizeof(int),1,fp,nullptr,error);
MPI_Bcast(&setflag[i][j],1,MPI_INT,0,world);
if (setflag[i][j]) {
if (me == 0) {
utils::sfread(FLERR,&J1_mag[i][j],sizeof(double),1,fp,nullptr,error);
utils::sfread(FLERR,&J1_mech[i][j],sizeof(double),1,fp,nullptr,error);
utils::sfread(FLERR,&J2[i][j],sizeof(double),1,fp,nullptr,error);
utils::sfread(FLERR,&J3[i][j],sizeof(double),1,fp,nullptr,error);
utils::sfread(FLERR,&K1_mag[i][j],sizeof(double),1,fp,nullptr,error);
utils::sfread(FLERR,&K1_mech[i][j],sizeof(double),1,fp,nullptr,error);
utils::sfread(FLERR,&K2[i][j],sizeof(double),1,fp,nullptr,error);
utils::sfread(FLERR,&K3[i][j],sizeof(double),1,fp,nullptr,error);
utils::sfread(FLERR,&cut_spin_exchange[i][j],sizeof(double),1,fp,nullptr,error);
}
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(&K1_mag[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&K1_mech[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&K2[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&K3[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 PairSpinExchangeBiquadratic::write_restart_settings(FILE *fp)
{
fwrite(&cut_spin_exchange_global,sizeof(double),1,fp);
fwrite(&e_offset,sizeof(int),1,fp);
fwrite(&offset_flag,sizeof(int),1,fp);
fwrite(&mix_flag,sizeof(int),1,fp);
}
/* ----------------------------------------------------------------------
proc 0 reads from restart file, bcasts
------------------------------------------------------------------------- */
void PairSpinExchangeBiquadratic::read_restart_settings(FILE *fp)
{
if (comm->me == 0) {
utils::sfread(FLERR,&cut_spin_exchange_global,sizeof(double),1,fp,nullptr,error);
utils::sfread(FLERR,&e_offset,sizeof(int),1,fp,nullptr,error);
utils::sfread(FLERR,&offset_flag,sizeof(int),1,fp,nullptr,error);
utils::sfread(FLERR,&mix_flag,sizeof(int),1,fp,nullptr,error);
}
MPI_Bcast(&cut_spin_exchange_global,1,MPI_DOUBLE,0,world);
MPI_Bcast(&e_offset,1,MPI_INT,0,world);
MPI_Bcast(&offset_flag,1,MPI_INT,0,world);
MPI_Bcast(&mix_flag,1,MPI_INT,0,world);
}
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