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lammps/src/SPIN/pair_spin_dipole_long.cpp
Axel Kohlmeyer 27da716852 getting out of the insurance business :-)
2023-01-23 16:45:41 -05:00

570 lines
16 KiB
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// clang-format off
/* ----------------------------------------------------------------------
LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
https://www.lammps.org/
LAMMPS development team: developers@lammps.org, Sandia National Laboratories
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)
Stan Moore (SNL)
------------------------------------------------------------------------- */
#include "pair_spin_dipole_long.h"
#include "atom.h"
#include "comm.h"
#include "error.h"
#include "force.h"
#include "kspace.h"
#include "math_const.h"
#include "memory.h"
#include "neigh_list.h"
#include <cmath>
#include <cstring>
using namespace LAMMPS_NS;
using namespace MathConst;
#define EWALD_F 1.12837917
#define EWALD_P 0.3275911
#define A1 0.254829592
#define A2 -0.284496736
#define A3 1.421413741
#define A4 -1.453152027
#define A5 1.061405429
/* ---------------------------------------------------------------------- */
PairSpinDipoleLong::PairSpinDipoleLong(LAMMPS *lmp) : PairSpin(lmp)
{
ewaldflag = pppmflag = spinflag = 1;
hbar = force->hplanck/MY_2PI; // eV/(rad.THz)
mub = 9.274e-4; // in A.Ang^2
mu_0 = 784.15; // in eV/Ang/A^2
mub2mu0 = mub * mub * mu_0 / (4.0*MY_PI); // in eV.Ang^3
//mub2mu0 = mub * mub * mu_0 / (4.0*MY_PI); // in eV
mub2mu0hbinv = mub2mu0 / hbar; // in rad.THz
}
/* ----------------------------------------------------------------------
free all arrays
------------------------------------------------------------------------- */
PairSpinDipoleLong::~PairSpinDipoleLong()
{
if (allocated) {
memory->destroy(setflag);
memory->destroy(cut_spin_long);
memory->destroy(cutsq);
memory->destroy(emag);
}
}
/* ----------------------------------------------------------------------
global settings
------------------------------------------------------------------------- */
void PairSpinDipoleLong::settings(int narg, char **arg)
{
PairSpin::settings(narg,arg);
cut_spin_long_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_long[i][j] = cut_spin_long_global;
}
}
}
}
}
/* ----------------------------------------------------------------------
set coeffs for one or more type pairs
------------------------------------------------------------------------- */
void PairSpinDipoleLong::coeff(int narg, char **arg)
{
if (!allocated) allocate();
if (narg != 3)
error->all(FLERR,"Incorrect args in pair_style command");
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);
double spin_long_cut_one = utils::numeric(FLERR,arg[2],false,lmp);
int count = 0;
for (int i = ilo; i <= ihi; i++) {
for (int j = MAX(jlo,i); j <= jhi; j++) {
setflag[i][j] = 1;
cut_spin_long[i][j] = spin_long_cut_one;
count++;
}
}
if (count == 0) error->all(FLERR,"Incorrect args for pair coefficients");
}
/* ----------------------------------------------------------------------
init specific to this pair style
------------------------------------------------------------------------- */
void PairSpinDipoleLong::init_style()
{
PairSpin::init_style();
// ensure use of KSpace long-range solver, set g_ewald
if (force->kspace == nullptr)
error->all(FLERR,"Pair style requires a KSpace style");
g_ewald = force->kspace->g_ewald;
}
/* ----------------------------------------------------------------------
init for one type pair i,j and corresponding j,i
------------------------------------------------------------------------- */
double PairSpinDipoleLong::init_one(int i, int j)
{
if (setflag[i][j] == 0) error->all(FLERR,"All pair coeffs are not set");
cut_spin_long[j][i] = cut_spin_long[i][j];
return cut_spin_long_global;
}
/* ----------------------------------------------------------------------
extract the larger cutoff if "cut" or "cut_coul"
------------------------------------------------------------------------- */
void *PairSpinDipoleLong::extract(const char *str, int &dim)
{
if (strcmp(str,"cut") == 0) {
dim = 0;
return (void *) &cut_spin_long_global;
} else if (strcmp(str,"cut_coul") == 0) {
dim = 0;
return (void *) &cut_spin_long_global;
} else if (strcmp(str,"ewald_order") == 0) {
ewald_order = 0;
ewald_order |= 1<<1;
ewald_order |= 1<<3;
dim = 0;
return (void *) &ewald_order;
} else if (strcmp(str,"ewald_mix") == 0) {
dim = 0;
return (void *) &mix_flag;
}
return nullptr;
}
/* ---------------------------------------------------------------------- */
void PairSpinDipoleLong::compute(int eflag, int vflag)
{
int i,j,ii,jj,inum,jnum,itype,jtype;
double r,rinv,r2inv,rsq;
double grij,expm2,t,erfc;
double evdwl,ecoul;
double bij[4];
double xi[3],rij[3],eij[3];
double spi[4],spj[4];
double fi[3],fmi[3];
double local_cut2;
double pre1,pre2,pre3;
int *ilist,*jlist,*numneigh,**firstneigh;
evdwl = ecoul = 0.0;
if (eflag || vflag) ev_setup(eflag,vflag);
else evflag = vflag_fdotr = 0;
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");
}
pre1 = 2.0 * g_ewald / MY_PIS;
pre2 = 4.0 * pow(g_ewald,3.0) / MY_PIS;
pre3 = 8.0 * pow(g_ewald,5.0) / MY_PIS;
// 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];
spi[3] = sp[i][3];
emag[i] = 0.0;
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];
spj[3] = sp[j][3];
evdwl = 0.0;
fi[0] = fi[1] = fi[2] = 0.0;
fmi[0] = fmi[1] = fmi[2] = 0.0;
bij[0] = bij[1] = bij[2] = bij[3] = 0.0;
rij[0] = x[j][0] - xi[0];
rij[1] = x[j][1] - xi[1];
rij[2] = x[j][2] - xi[2];
rsq = rij[0]*rij[0] + rij[1]*rij[1] + rij[2]*rij[2];
rinv = 1.0/sqrt(rsq);
eij[0] = rij[0]*rinv;
eij[1] = rij[1]*rinv;
eij[2] = rij[2]*rinv;
local_cut2 = cut_spin_long[itype][jtype]*cut_spin_long[itype][jtype];
if (rsq < local_cut2) {
r2inv = 1.0/rsq;
r = sqrt(rsq);
grij = g_ewald * r;
expm2 = exp(-grij*grij);
t = 1.0 / (1.0 + EWALD_P*grij);
erfc = t * (A1+t*(A2+t*(A3+t*(A4+t*A5)))) * expm2;
bij[0] = erfc * rinv;
bij[1] = (bij[0] + pre1*expm2) * r2inv;
bij[2] = (3.0*bij[1] + pre2*expm2) * r2inv;
bij[3] = (5.0*bij[2] + pre3*expm2) * r2inv;
compute_long(i,j,eij,bij,fmi,spi,spj);
if (lattice_flag)
compute_long_mech(i,j,eij,bij,fmi,spi,spj);
if (eflag) {
if (rsq <= local_cut2) {
evdwl -= (spi[0]*fmi[0] + spi[1]*fmi[1] + spi[2]*fmi[2]);
evdwl *= 0.5*hbar;
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],rij[0],rij[1],rij[2]);
}
}
}
if (vflag_fdotr) virial_fdotr_compute();
}
/* ----------------------------------------------------------------------
update the pair interaction fmi acting on the spin ii
------------------------------------------------------------------------- */
void PairSpinDipoleLong::compute_single_pair(int ii, double fmi[3])
{
int j,jj,jnum,itype,jtype,ntypes;
int k,locflag;
int *jlist,*numneigh,**firstneigh;
double r,rinv,r2inv,rsq,grij,expm2,t,erfc;
double local_cut2,pre1,pre2,pre3;
double bij[4],xi[3],rij[3],eij[3],spi[4],spj[4];
int *type = atom->type;
double **x = atom->x;
double **sp = atom->sp;
double **fm_long = atom->fm_long;
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) {
pre1 = 2.0 * g_ewald / MY_PIS;
pre2 = 4.0 * pow(g_ewald,3.0) / MY_PIS;
pre3 = 8.0 * pow(g_ewald,5.0) / MY_PIS;
// computation of the exchange interaction
// loop over neighbors of atom i
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];
spi[3] = sp[ii][3];
jlist = firstneigh[ii];
jnum = numneigh[ii];
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];
spj[3] = sp[j][3];
fmi[0] = fmi[1] = fmi[2] = 0.0;
bij[0] = bij[1] = bij[2] = bij[3] = 0.0;
rij[0] = x[j][0] - xi[0];
rij[1] = x[j][1] - xi[1];
rij[2] = x[j][2] - xi[2];
rsq = rij[0]*rij[0] + rij[1]*rij[1] + rij[2]*rij[2];
rinv = 1.0/sqrt(rsq);
eij[0] = rij[0]*rinv;
eij[1] = rij[1]*rinv;
eij[2] = rij[2]*rinv;
local_cut2 = cut_spin_long[itype][jtype]*cut_spin_long[itype][jtype];
if (rsq < local_cut2) {
r2inv = 1.0/rsq;
r = sqrt(rsq);
grij = g_ewald * r;
expm2 = exp(-grij*grij);
t = 1.0 / (1.0 + EWALD_P*grij);
erfc = t * (A1+t*(A2+t*(A3+t*(A4+t*A5)))) * expm2;
bij[0] = erfc * rinv;
bij[1] = (bij[0] + pre1*expm2) * r2inv;
bij[2] = (3.0*bij[1] + pre2*expm2) * r2inv;
bij[3] = (5.0*bij[2] + pre3*expm2) * r2inv;
compute_long(ii,j,eij,bij,fmi,spi,spj);
}
}
// adding the kspace components to fm
fmi[0] += fm_long[ii][0];
fmi[1] += fm_long[ii][1];
fmi[2] += fm_long[ii][2];
}
}
/* ----------------------------------------------------------------------
compute dipolar interaction between spins i and j
------------------------------------------------------------------------- */
void PairSpinDipoleLong::compute_long(int /* i */, int /* j */, double eij[3],
double bij[4], double fmi[3], double spi[4], double spj[4])
{
double sjeij,pre;
double b1,b2,gigj;
gigj = spi[3] * spj[3];
pre = gigj*mub2mu0hbinv;
sjeij = spj[0]*eij[0] + spj[1]*eij[1] + spj[2]*eij[2];
b1 = bij[1];
b2 = bij[2];
fmi[0] += pre * (b2 * sjeij * eij[0] - b1 * spj[0]);
fmi[1] += pre * (b2 * sjeij * eij[1] - b1 * spj[1]);
fmi[2] += pre * (b2 * sjeij * eij[2] - b1 * spj[2]);
}
/* ----------------------------------------------------------------------
compute the mechanical force due to the dipolar interaction between
atom i and atom j
------------------------------------------------------------------------- */
void PairSpinDipoleLong::compute_long_mech(int /* i */, int /* j */, double eij[3],
double bij[4], double fi[3], double spi[4], double spj[4])
{
double sisj,sieij,sjeij,b2,b3;
double g1,g2,g1b2_g2b3,gigj,pre;
gigj = spi[3] * spj[3];
pre = 0.5 * gigj*mub2mu0;
sisj = spi[0]*spj[0] + spi[1]*spj[1] + spi[2]*spj[2];
sieij = spi[0]*eij[0] + spi[1]*eij[1] + spi[2]*eij[2];
sjeij = spj[0]*eij[0] + spj[1]*eij[1] + spj[2]*eij[2];
b2 = bij[2];
b3 = bij[3];
g1 = sisj;
g2 = -sieij*sjeij;
g1b2_g2b3 = g1*b2 + g2*b3;
fi[0] += pre * (eij[0] * g1b2_g2b3 + b2 * (sjeij*spi[0] + sieij*spj[0]));
fi[1] += pre * (eij[1] * g1b2_g2b3 + b2 * (sjeij*spi[1] + sieij*spj[1]));
fi[2] += pre * (eij[2] * g1b2_g2b3 + b2 * (sjeij*spi[2] + sieij*spj[2]));
}
/* ----------------------------------------------------------------------
allocate all arrays
------------------------------------------------------------------------- */
void PairSpinDipoleLong::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_long,n+1,n+1,"pair/spin/long:cut_spin_long");
memory->create(cutsq,n+1,n+1,"pair/spin/long:cutsq");
}
/* ----------------------------------------------------------------------
proc 0 writes to restart file
------------------------------------------------------------------------- */
void PairSpinDipoleLong::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(&cut_spin_long[i][j],sizeof(int),1,fp);
}
}
}
}
/* ----------------------------------------------------------------------
proc 0 reads from restart file, bcasts
------------------------------------------------------------------------- */
void PairSpinDipoleLong::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,&cut_spin_long[i][j],sizeof(int),1,fp,nullptr,error);
}
MPI_Bcast(&cut_spin_long[i][j],1,MPI_DOUBLE,0,world);
}
}
}
}
/* ----------------------------------------------------------------------
proc 0 writes to restart file
------------------------------------------------------------------------- */
void PairSpinDipoleLong::write_restart_settings(FILE *fp)
{
fwrite(&cut_spin_long_global,sizeof(double),1,fp);
fwrite(&mix_flag,sizeof(int),1,fp);
}
/* ----------------------------------------------------------------------
proc 0 reads from restart file, bcasts
------------------------------------------------------------------------- */
void PairSpinDipoleLong::read_restart_settings(FILE *fp)
{
if (comm->me == 0) {
utils::sfread(FLERR,&cut_spin_long_global,sizeof(double),1,fp,nullptr,error);
utils::sfread(FLERR,&mix_flag,sizeof(int),1,fp,nullptr,error);
}
MPI_Bcast(&cut_spin_long_global,1,MPI_DOUBLE,0,world);
MPI_Bcast(&mix_flag,1,MPI_INT,0,world);
}
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