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fix_temp_rescale.cpp
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Sun, Nov 3, 22:47

fix_temp_rescale.cpp
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/* ----------------------------------------------------------------------
LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
www.cs.sandia.gov/~sjplimp/lammps.html
Steve Plimpton, sjplimp@sandia.gov, Sandia National Laboratories
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 "string.h"
#include "stdlib.h"
#include "math.h"
#include "fix_temp_rescale.h"
#include "atom.h"
#include "force.h"
#include "group.h"
#include "update.h"
#include "domain.h"
#include "region.h"
#include "comm.h"
#include "temperature.h"
#include "error.h"
/* ---------------------------------------------------------------------- */
FixTempRescale::FixTempRescale(int narg, char **arg) : Fix(narg, arg)
{
if (narg < 8) error->all("Illegal fix temp/rescale command");
nevery = atoi(arg[3]);
if (nevery <= 0) error->all("Illegal fix temp/rescale command");
t_start = atof(arg[4]);
t_end = atof(arg[5]);
t_window = atof(arg[6]);
fraction = atof(arg[7]);
// optional args
iregion = -1;
int iarg = 8;
while (iarg < narg) {
if (strcmp(arg[iarg],"region") == 0) {
for (iregion = 0; iregion < domain->nregion; iregion++)
if (strcmp(arg[iarg+1],domain->regions[iregion]->id) == 0) break;
if (iregion == domain->nregion)
error->all("Fix temp/rescale region ID does not exist");
iarg += 2;
} else error->all("Illegal fix temp/rescale command");
}
// create a new temperature full or region style with fix ID and fix group
char **newarg = new char*[4];
newarg[0] = id;
newarg[1] = group->names[igroup];
if (iregion == -1) {
newarg[2] = "full";
force->add_temp(3,newarg,1);
} else {
newarg[2] = "region";
newarg[3] = domain->regions[iregion]->id;
force->add_temp(4,newarg,1);
}
delete [] newarg;
temperature = force->find_temp(id);
}
/* ---------------------------------------------------------------------- */
int FixTempRescale::setmask()
{
int mask = 0;
mask |= END_OF_STEP;
mask |= THERMO;
return mask;
}
/* ---------------------------------------------------------------------- */
void FixTempRescale::init()
{
energy = 0.0;
efactor = (0.5 * force->boltz * temperature->dof);
}
/* ---------------------------------------------------------------------- */
void FixTempRescale::end_of_step()
{
double t_current = temperature->compute();
double delta = update->ntimestep - update->beginstep;
delta /= update->endstep - update->beginstep;
double t_target = t_start + delta * (t_end-t_start);
if (fabs(t_current-t_target) > t_window) {
t_target = t_current - fraction*(t_current-t_target);
double factor = sqrt(t_target/t_current);
double **x = atom->x;
double **v = atom->v;
int *mask = atom->mask;
int nlocal = atom->nlocal;
if (iregion == -1) {
energy += (t_current-t_target) * efactor;
for (int i = 0; i < nlocal; i++) {
if (mask[i] & groupbit) {
v[i][0] *= factor;
v[i][1] *= factor;
v[i][2] *= factor;
}
}
} else {
efactor = (0.5 * force->boltz * temperature->dof);
energy += (t_current-t_target) * efactor;
for (int i = 0; i < nlocal; i++) {
if (mask[i] & groupbit &&
domain->regions[iregion]->match(x[i][0],x[i][1],x[i][2])) {
v[i][0] *= factor;
v[i][1] *= factor;
v[i][2] *= factor;
}
}
}
} else energy = 0.0;
}
/* ---------------------------------------------------------------------- */
int FixTempRescale::modify_param(int narg, char **arg)
{
if (strcmp(arg[0],"temp") == 0) {
if (narg < 2) error->all("Illegal fix_modify command");
temperature = force->find_temp(arg[1]);
if (temperature == NULL)
error->all("Could not find fix_modify temperature ID");
if (temperature->igroup != igroup && comm->me == 0)
error->warning("Group for fix_modify temp != fix group");
if (strcmp(temperature->style,"region") == 0 && iregion == -1 &&
comm->me == 0)
error->warning("Temperature for temp/rescale is style region");
return 2;
}
return 0;
}
/* ---------------------------------------------------------------------- */
int FixTempRescale::thermo_fields(int n, int *flags, char **keywords)
{
if (n == 0) return 1;
flags[0] = 3;
strcpy(keywords[0],"EngTRscl");
return 1;
}
/* ---------------------------------------------------------------------- */
int FixTempRescale::thermo_compute(double *values)
{
values[0] = energy;
return 1;
}

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