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compute_rotate_dipole.cpp
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Sat, Aug 10, 11:11

compute_rotate_dipole.cpp
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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.
------------------------------------------------------------------------- */
#include "mpi.h"
#include "compute_rotate_dipole.h"
#include "atom.h"
#include "force.h"
#include "pair.h"
#include "group.h"
#include "error.h"
using namespace LAMMPS_NS;
#define INERTIA3D 0.4 // moments of inertia for sphere and disk
#define INERTIA2D 0.5
/* ---------------------------------------------------------------------- */
ComputeRotateDipole::ComputeRotateDipole(LAMMPS *lmp, int narg, char **arg) :
Compute(lmp, narg, arg)
{
if (narg != 3) error->all("Illegal compute rotate/dipole command");
if (atom->check_style("dipole") == 0)
error->all("Must use atom style dipole with compute rotate/dipole");
scalar_flag = 1;
extensive = 1;
inertia = NULL;
}
/* ---------------------------------------------------------------------- */
ComputeRotateDipole::~ComputeRotateDipole()
{
delete [] inertia;
}
/* ---------------------------------------------------------------------- */
void ComputeRotateDipole::init()
{
delete [] inertia;
inertia = new double[atom->ntypes+1];
double *mass = atom->mass;
// insure use of dipole pair_style
// set sigma to Pair's sigma
Pair *pair = force->pair_match("dipole");
if (pair == NULL)
error->all("Pair style is incompatible with compute rotate/dipole");
double **sigma;
pair->extract_dipole(&sigma);
if (force->dimension == 3)
for (int i = 1; i <= atom->ntypes; i++)
inertia[i] = INERTIA3D * mass[i] * 0.25*sigma[i][i]*sigma[i][i];
else
for (int i = 1; i <= atom->ntypes; i++)
inertia[i] = INERTIA2D * mass[i] * 0.25*sigma[i][i]*sigma[i][i];
}
/* ---------------------------------------------------------------------- */
double ComputeRotateDipole::compute_scalar()
{
double *dipole = atom->dipole;
double **omega = atom->omega;
int *type = atom->type;
int *mask = atom->mask;
int nlocal = atom->nlocal;
double erot = 0.0;
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit && dipole[type[i]] > 0.0)
erot += inertia[type[i]] *
(omega[i][0]*omega[i][0] + omega[i][1]*omega[i][1] +
omega[i][2]*omega[i][2]);
MPI_Allreduce(&erot,&scalar,1,MPI_DOUBLE,MPI_SUM,world);
scalar *= 0.5;
return scalar;
}

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