252 lines
6.9 KiB
C++
252 lines
6.9 KiB
C++
// clang-format off
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/* ----------------------------------------------------------------------
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LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
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https://www.lammps.org/, Sandia National Laboratories
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Steve Plimpton, sjplimp@sandia.gov
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Copyright (2003) Sandia Corporation. Under the terms of Contract
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DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
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certain rights in this software. This software is distributed under
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the GNU General Public License.
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See the README file in the top-level LAMMPS directory.
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------------------------------------------------------------------------- */
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/* ------------------------------------------------------------------------
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Contributing authors: Julien Tranchida (SNL)
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Aidan Thompson (SNL)
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Please cite the related publication:
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Tranchida, J., Plimpton, S. J., Thibaudeau, P., & Thompson, A. P. (2018).
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Massively parallel symplectic algorithm for coupled magnetic spin dynamics
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and molecular dynamics. Journal of Computational Physics.
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------------------------------------------------------------------------- */
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#include "compute_spin.h"
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#include "atom.h"
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#include "error.h"
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#include "fix_precession_spin.h"
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#include "force.h"
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#include "math_const.h"
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#include "memory.h"
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#include "modify.h"
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#include "pair_hybrid.h"
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#include "pair_spin.h"
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#include "update.h"
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#include <cmath>
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using namespace LAMMPS_NS;
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using namespace MathConst;
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/* ---------------------------------------------------------------------- */
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ComputeSpin::ComputeSpin(LAMMPS *lmp, int narg, char **arg) :
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Compute(lmp, narg, arg), pair(nullptr), spin_pairs(nullptr)
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{
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if ((narg != 3) && (narg != 4)) error->all(FLERR,"Illegal compute compute/spin command");
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vector_flag = 1;
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size_vector = 6;
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extvector = 0;
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// initialize the magnetic interaction flags
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pair_spin_flag = 0;
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long_spin_flag = 0;
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precession_spin_flag = 0;
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ComputeSpin::init();
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allocate();
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}
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/* ---------------------------------------------------------------------- */
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ComputeSpin::~ComputeSpin()
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{
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memory->destroy(vector);
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delete [] spin_pairs;
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}
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/* ---------------------------------------------------------------------- */
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void ComputeSpin::init()
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{
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hbar = force->hplanck/MY_2PI;
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kb = force->boltz;
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npairs = npairspin = 0;
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precession_spin_flag = 0;
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// set ptrs on Pair/Spin styles
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// loop 1: obtain # of Pairs, and # of Pair/Spin styles
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PairHybrid *hybrid = (PairHybrid *)force->pair_match("^hybrid",0);
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if (force->pair_match("^spin",0,0)) { // only one Pair/Spin style
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pair = force->pair_match("^spin",0,0);
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if (hybrid == nullptr) npairs = 1;
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else npairs = hybrid->nstyles;
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npairspin = 1;
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} else if (force->pair_match("^spin",0,1)) { // more than one Pair/Spin style
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pair = force->pair_match("^spin",0,1);
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if (hybrid == nullptr) npairs = 1;
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else npairs = hybrid->nstyles;
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for (int i = 0; i<npairs; i++) {
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if (force->pair_match("^spin",0,i)) {
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npairspin ++;
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}
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}
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}
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// init length of vector of ptrs to Pair/Spin styles
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if (npairspin > 0) {
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spin_pairs = new PairSpin*[npairspin];
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}
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// loop 2: fill vector with ptrs to Pair/Spin styles
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int count = 0;
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if (npairspin == 1) {
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count = 1;
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spin_pairs[0] = (PairSpin *) force->pair_match("^spin",0,0);
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} else if (npairspin > 1) {
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for (int i = 0; i<npairs; i++) {
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if (force->pair_match("^spin",0,i)) {
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spin_pairs[count] = (PairSpin *) force->pair_match("^spin",0,i);
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count++;
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}
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}
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}
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if (count != npairspin)
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error->all(FLERR,"Incorrect number of spin pair styles");
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// set pair/spin and long/spin flags
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if (npairspin >= 1) pair_spin_flag = 1;
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for (int i = 0; i<npairs; i++) {
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if (force->pair_match("^spin/long",0,i)) {
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long_spin_flag = 1;
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}
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}
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// ptrs FixPrecessionSpin classes
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int iforce;
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for (iforce = 0; iforce < modify->nfix; iforce++) {
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if (utils::strmatch(modify->fix[iforce]->style,"^precession/spin")) {
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precession_spin_flag = 1;
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lockprecessionspin = (FixPrecessionSpin *) modify->fix[iforce];
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}
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}
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}
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/* ---------------------------------------------------------------------- */
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void ComputeSpin::compute_vector()
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{
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int i;
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int countsp, countsptot;
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double mag[4], magtot[4];
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double magenergy, magenergytot;
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double tempnum, tempnumtot;
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double tempdenom, tempdenomtot;
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double spintemperature;
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invoked_vector = update->ntimestep;
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countsp = countsptot = 0.0;
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mag[0] = mag[1] = mag[2] = mag[3] = 0.0;
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magtot[0] = magtot[1] = magtot[2] = magtot[3] = 0.0;
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magenergy = magenergytot = 0.0;
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tempnum = tempnumtot = 0.0;
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tempdenom = tempdenomtot = 0.0;
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spintemperature = 0.0;
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int *mask = atom->mask;
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double **sp = atom->sp;
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double **fm = atom->fm;
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double tx,ty,tz;
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int nlocal = atom->nlocal;
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// compute total magnetization and magnetic energy
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// compute spin temperature (Nurdin et al., Phys. Rev. E 61, 2000)
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for (i = 0; i < nlocal; i++) {
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if (mask[i] & groupbit) {
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if (atom->sp_flag) {
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// compute first moment
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mag[0] += sp[i][0];
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mag[1] += sp[i][1];
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mag[2] += sp[i][2];
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// update magnetic precession energies
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if (precession_spin_flag) {
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magenergy += lockprecessionspin->emag[i];
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}
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// update magnetic pair interactions
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if (pair_spin_flag) {
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for (int k = 0; k < npairspin; k++) {
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magenergy += spin_pairs[k]->emag[i];
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}
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}
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tx = sp[i][1]*fm[i][2]-sp[i][2]*fm[i][1];
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ty = sp[i][2]*fm[i][0]-sp[i][0]*fm[i][2];
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tz = sp[i][0]*fm[i][1]-sp[i][1]*fm[i][0];
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tempnum += tx*tx+ty*ty+tz*tz;
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tempdenom += sp[i][0]*fm[i][0]+fm[i][1]*sp[i][1]+sp[i][2]*fm[i][2];
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countsp++;
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}
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}
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else error->all(FLERR,"Compute compute/spin requires atom/spin style");
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}
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MPI_Allreduce(mag,magtot,4,MPI_DOUBLE,MPI_SUM,world);
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MPI_Allreduce(&magenergy,&magenergytot,1,MPI_DOUBLE,MPI_SUM,world);
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MPI_Allreduce(&tempnum,&tempnumtot,1,MPI_DOUBLE,MPI_SUM,world);
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MPI_Allreduce(&tempdenom,&tempdenomtot,1,MPI_DOUBLE,MPI_SUM,world);
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MPI_Allreduce(&countsp,&countsptot,1,MPI_INT,MPI_SUM,world);
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// compute average magnetization
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double scale = 1.0/countsptot;
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magtot[0] *= scale;
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magtot[1] *= scale;
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magtot[2] *= scale;
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magtot[3] = sqrt((magtot[0]*magtot[0])+(magtot[1]*magtot[1])+(magtot[2]*magtot[2]));
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// compute spin temperature
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spintemperature = hbar*tempnumtot;
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spintemperature /= (2.0*kb*tempdenomtot);
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vector[0] = magtot[0];
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vector[1] = magtot[1];
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vector[2] = magtot[2];
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vector[3] = magtot[3];
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vector[4] = magenergytot;
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vector[5] = spintemperature;
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}
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/* ----------------------------------------------------------------------
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free and reallocate arrays
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------------------------------------------------------------------------- */
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void ComputeSpin::allocate()
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{
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memory->create(vector,size_vector,"compute/spin:vector");
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}
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