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fix_efield.cpp
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Sun, Jun 29, 12:33

fix_efield.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.
------------------------------------------------------------------------- */
/* ----------------------------------------------------------------------
Contributing author: Christina Payne (Vanderbilt U)
------------------------------------------------------------------------- */
#include "string.h"
#include "stdlib.h"
#include "fix_efield.h"
#include "atom.h"
#include "update.h"
#include "force.h"
#include "respa.h"
#include "error.h"
#include "math.h"
using namespace LAMMPS_NS;
/* ---------------------------------------------------------------------- */
FixEfield::FixEfield(LAMMPS *lmp, int narg, char **arg) :
Fix(lmp, narg, arg)
{
if (narg != 6) error->all("Illegal fix efield command");
double factor = force->qe2f;
ex = factor * atof(arg[3]);
ey = factor * atof(arg[4]);
ez = factor * atof(arg[5]);
}
/* ---------------------------------------------------------------------- */
int FixEfield::setmask()
{
int mask = 0;
mask |= POST_FORCE;
mask |= POST_FORCE_RESPA;
return mask;
}
/* ---------------------------------------------------------------------- */
void FixEfield::init()
{
// require an atom style with charge defined
if (atom->q == NULL)
error->all("Must use charged atom style with fix efield");
if (strcmp(update->integrate_style,"respa") == 0)
nlevels_respa = ((Respa *) update->integrate)->nlevels;
}
/* ---------------------------------------------------------------------- */
void FixEfield::setup(int vflag)
{
if (strcmp(update->integrate_style,"verlet") == 0)
post_force(vflag);
else {
((Respa *) update->integrate)->copy_flevel_f(nlevels_respa-1);
post_force_respa(vflag,nlevels_respa-1,0);
((Respa *) update->integrate)->copy_f_flevel(nlevels_respa-1);
}
}
/* ----------------------------------------------------------------------
apply F = qE
------------------------------------------------------------------------- */
void FixEfield::post_force(int vflag)
{
double **f = atom->f;
double *q = atom->q;
int *mask = atom->mask;
int nlocal = atom->nlocal;
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
f[i][0] += q[i]*ex;
f[i][1] += q[i]*ey;
f[i][2] += q[i]*ez;
}
}
/* ---------------------------------------------------------------------- */
void FixEfield::post_force_respa(int vflag, int ilevel, int iloop)
{
if (ilevel == nlevels_respa-1) post_force(vflag);
}

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