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fix_nve_eff.cpp
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Fri, Nov 1, 03:01

fix_nve_eff.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: Andres Jaramillo-Botero (Caltech)
------------------------------------------------------------------------- */
#include "math.h"
#include "stdio.h"
#include "string.h"
#include "fix_nve_eff.h"
#include "atom.h"
#include "force.h"
#include "update.h"
#include "respa.h"
#include "error.h"
#include "math.h"
using namespace LAMMPS_NS;
/* ---------------------------------------------------------------------- */
FixNVEEff::FixNVEEff(LAMMPS *lmp, int narg, char **arg) :
Fix(lmp, narg, arg)
{
if (!atom->electron_flag)
error->all("Fix nve/eff requires atom style electron");
time_integrate = 1;
}
/* ---------------------------------------------------------------------- */
int FixNVEEff::setmask()
{
int mask = 0;
mask |= INITIAL_INTEGRATE;
mask |= FINAL_INTEGRATE;
mask |= INITIAL_INTEGRATE_RESPA;
mask |= FINAL_INTEGRATE_RESPA;
return mask;
}
/* ---------------------------------------------------------------------- */
void FixNVEEff::init()
{
dtv = update->dt;
dtf = 0.5 * update->dt * force->ftm2v;
if (strcmp(update->integrate_style,"respa") == 0)
step_respa = ((Respa *) update->integrate)->step;
}
/* ----------------------------------------------------------------------
allow for both per-type and per-atom mass
------------------------------------------------------------------------- */
void FixNVEEff::initial_integrate(int vflag)
{
double dtfm;
// update v,vr and x,radius of atoms in group
double **x = atom->x;
double *eradius = atom->eradius;
double **v = atom->v;
double *ervel = atom->ervel;
double **f = atom->f;
double *erforce = atom->erforce;
double *mass = atom->mass;
int *spin = atom->spin;
int *type = atom->type;
int *mask = atom->mask;
int nlocal = atom->nlocal;
if (igroup == atom->firstgroup) nlocal = atom->nfirst;
// x + dt * [v + 0.5 * dt * (f / m)];
if (mass) {
for (int i = 0; i < nlocal; i++) {
if (mask[i] & groupbit) {
dtfm = dtf / mass[type[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];
if (fabs(spin[i])==1) {
ervel[i] += dtfm * erforce[i] / 0.75;
eradius[i] += dtv * ervel[i];
}
}
}
}
}
/* ---------------------------------------------------------------------- */
void FixNVEEff::final_integrate()
{
double dtfm;
double **v = atom->v;
double *ervel = atom->ervel;
double *erforce = atom->erforce;
double **f = atom->f;
double *mass = atom->mass;
int *spin = atom->spin;
int *type = atom->type;
int *mask = atom->mask;
int nlocal = atom->nlocal;
if (igroup == atom->firstgroup) nlocal = atom->nfirst;
// dyn_v[i] += m * dt * dyn_f[i];
if (mass) {
for (int i = 0; i < nlocal; i++) {
if (mask[i] & groupbit) {
dtfm = dtf / mass[type[i]];
v[i][0] += dtfm * f[i][0];
v[i][1] += dtfm * f[i][1];
v[i][2] += dtfm * f[i][2];
if (fabs(spin[i])==1)
ervel[i] += dtfm * erforce[i] / 0.75;
}
}
}
}
/* ---------------------------------------------------------------------- */
void FixNVEEff::initial_integrate_respa(int vflag, int ilevel, int iloop)
{
dtv = step_respa[ilevel];
dtf = 0.5 * step_respa[ilevel] * force->ftm2v;
// innermost level - NVE update of v and x
// all other levels - NVE update of v
if (ilevel == 0) initial_integrate(vflag);
else final_integrate();
}
/* ---------------------------------------------------------------------- */
void FixNVEEff::final_integrate_respa(int ilevel, int iloop)
{
dtf = 0.5 * step_respa[ilevel] * force->ftm2v;
final_integrate();
}
/* ---------------------------------------------------------------------- */
void FixNVEEff::reset_dt()
{
dtv = update->dt;
dtf = 0.5 * update->dt * force->ftm2v;
}

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