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lammps/src/GRANULAR/fix_nve_gran.cpp
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fix_nve_gran.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 "stdio.h"
#include "string.h"
#include "fix_nve_gran.h"
#include "atom.h"
#include "update.h"
#include "force.h"
#include "domain.h"
#include "error.h"
using namespace LAMMPS_NS;
// moments of inertia for sphere and disk
#define INERTIA3D 0.4
#define INERTIA2D 0.5
/* ---------------------------------------------------------------------- */
FixNVEGran::FixNVEGran(LAMMPS *lmp, int narg, char **arg) :
Fix(lmp, narg, arg)
{
if (narg != 3) error->all("Illegal fix nve/gran command");
if (!atom->xorient_flag || !atom->omega_flag || !atom->torque_flag)
error->all("Fix nve/gran requires atom attributes "
"xorient, omega, torque");
}
/* ---------------------------------------------------------------------- */
int FixNVEGran::setmask()
{
int mask = 0;
mask |= INITIAL_INTEGRATE;
mask |= FINAL_INTEGRATE;
return mask;
}
/* ---------------------------------------------------------------------- */
void FixNVEGran::init()
{
dtv = update->dt;
dtf = 0.5 * update->dt * force->ftm2v;
if (domain->dimension == 3) dtfrotate = dtf / INERTIA3D;
else dtfrotate = dtf / INERTIA2D;
}
/* ---------------------------------------------------------------------- */
void FixNVEGran::initial_integrate()
{
double dtfm;
double **x = atom->x;
double **v = atom->v;
double **f = atom->f;
double **xorient = atom->xorient;
double **omega = atom->omega;
double **torque = atom->torque;
double *rmass = atom->rmass;
double *radius = atom->radius;
int *mask = atom->mask;
int nlocal = atom->nlocal;
for (int i = 0; i < nlocal; i++) {
if (mask[i] & groupbit) {
dtfm = dtf / rmass[i];
v[i][0] += dtfm * f[i][0];
v[i][1] += dtfm * f[i][1];
v[i][2] += dtfm * f[i][2];
x[i][0] += dtv * v[i][0];
x[i][1] += dtv * v[i][1];
x[i][2] += dtv * v[i][2];
dtfm = dtfrotate / (radius[i]*radius[i]*rmass[i]);
omega[i][0] += dtfm * torque[i][0];
omega[i][1] += dtfm * torque[i][1];
omega[i][2] += dtfm * torque[i][2];
xorient[i][0] += dtv * omega[i][0];
xorient[i][1] += dtv * omega[i][1];
xorient[i][2] += dtv * omega[i][2];
}
}
}
/* ---------------------------------------------------------------------- */
void FixNVEGran::final_integrate()
{
double dtfm;
double **v = atom->v;
double **f = atom->f;
double **omega = atom->omega;
double **torque = atom->torque;
double *rmass = atom->rmass;
double *radius = atom->radius;
int *mask = atom->mask;
int nlocal = atom->nlocal;
for (int i = 0; i < nlocal; i++) {
if (mask[i] & groupbit) {
dtfm = dtf / rmass[i];
v[i][0] += dtfm * f[i][0];
v[i][1] += dtfm * f[i][1];
v[i][2] += dtfm * f[i][2];
dtfm = dtfrotate / (radius[i]*radius[i]*rmass[i]);
omega[i][0] += dtfm * torque[i][0];
omega[i][1] += dtfm * torque[i][1];
omega[i][2] += dtfm * torque[i][2];
}
}
}
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