155 lines
4.5 KiB
C++
155 lines
4.5 KiB
C++
/* ----------------------------------------------------------------------
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LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
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http://lammps.sandia.gov, 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 <mpi.h>
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#include <cstring>
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#include "atom.h"
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#include "compute_spin.h"
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#include "domain.h"
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#include "error.h"
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#include "force.h"
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#include "math_special.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 "update.h"
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using namespace LAMMPS_NS;
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using namespace MathSpecial;
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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)
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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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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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}
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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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}
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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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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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magenergy -= (sp[i][0]*fm[i][0] + sp[i][1]*fm[i][1] + sp[i][2]*fm[i][2]);
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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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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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spintemperature = hbar*tempnumtot;
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spintemperature /= (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*hbar;
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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,6,"compute/spin:vector");
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}
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