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compute_pressure_grem.cpp
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Sat, Nov 9, 08:18

compute_pressure_grem.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 <string.h>
#include <stdlib.h>
#include "compute_pressure_grem.h"
#include "atom.h"
#include "update.h"
#include "domain.h"
#include "modify.h"
#include "fix.h"
#include "force.h"
#include "pair.h"
#include "kspace.h"
#include "error.h"
using namespace LAMMPS_NS;
/* ----------------------------------------------------------------------
Last argument is the id of the gREM fix
------------------------------------------------------------------------- */
ComputePressureGrem::ComputePressureGrem(LAMMPS *lmp, int narg, char **arg) :
ComputePressure(lmp, narg-1, arg)
{
int len = strlen(arg[narg-1])+1;
fix_grem = new char[len];
strcpy(fix_grem,arg[narg-1]);
}
/* ---------------------------------------------------------------------- */
ComputePressureGrem::~ComputePressureGrem()
{
delete [] fix_grem;
}
/* ---------------------------------------------------------------------- */
void ComputePressureGrem::init()
{
ComputePressure::init();
// Initialize hook to gREM fix
int ifix = modify->find_fix(fix_grem);
if (ifix < 0)
error->all(FLERR,"Fix grem ID for compute PRESSURE/GREM does not exist");
int dim;
scale_grem = (double *)modify->fix[ifix]->extract("scale_grem",dim);
if (scale_grem == NULL || dim != 0)
error->all(FLERR,"Cannot extract gREM scale factor from fix grem");
}
/* ----------------------------------------------------------------------
compute total pressure, averaged over Pxx, Pyy, Pzz
------------------------------------------------------------------------- */
double ComputePressureGrem::compute_scalar()
{
invoked_scalar = update->ntimestep;
if (update->vflag_global != invoked_scalar)
error->all(FLERR,"Virial was not tallied on needed timestep");
// invoke temperature if it hasn't been already
double t;
if (keflag) {
if (temperature->invoked_scalar != update->ntimestep)
t = temperature->compute_scalar() / (*scale_grem);
else t = temperature->scalar / (*scale_grem);
}
if (dimension == 3) {
inv_volume = 1.0 / (domain->xprd * domain->yprd * domain->zprd);
virial_compute(3,3);
if (keflag)
scalar = (temperature->dof * boltz * t +
virial[0] + virial[1] + virial[2]) / 3.0 * inv_volume * nktv2p;
else
scalar = (virial[0] + virial[1] + virial[2]) / 3.0 * inv_volume * nktv2p;
} else {
inv_volume = 1.0 / (domain->xprd * domain->yprd);
virial_compute(2,2);
if (keflag)
scalar = (temperature->dof * boltz * t +
virial[0] + virial[1]) / 2.0 * inv_volume * nktv2p;
else
scalar = (virial[0] + virial[1]) / 2.0 * inv_volume * nktv2p;
}
return scalar;
}
/* ----------------------------------------------------------------------
compute pressure tensor
assume KE tensor has already been computed
------------------------------------------------------------------------- */
void ComputePressureGrem::compute_vector()
{
invoked_vector = update->ntimestep;
if (update->vflag_global != invoked_vector)
error->all(FLERR,"Virial was not tallied on needed timestep");
if (force->kspace && kspace_virial && force->kspace->scalar_pressure_flag)
error->all(FLERR,"Must use 'kspace_modify pressure/scalar no' for "
"tensor components with kspace_style msm");
// invoke temperature if it hasn't been already
double ke_tensor[6];
if (keflag) {
if (temperature->invoked_vector != update->ntimestep)
temperature->compute_vector();
for (int i = 0; i < 6; ++i)
ke_tensor[i] = temperature->vector[i] / (*scale_grem);
}
if (dimension == 3) {
inv_volume = 1.0 / (domain->xprd * domain->yprd * domain->zprd);
virial_compute(6,3);
if (keflag) {
for (int i = 0; i < 6; i++)
vector[i] = (ke_tensor[i] + virial[i]) * inv_volume * nktv2p;
} else
for (int i = 0; i < 6; i++)
vector[i] = virial[i] * inv_volume * nktv2p;
} else {
inv_volume = 1.0 / (domain->xprd * domain->yprd);
virial_compute(4,2);
if (keflag) {
vector[0] = (ke_tensor[0] + virial[0]) * inv_volume * nktv2p;
vector[1] = (ke_tensor[1] + virial[1]) * inv_volume * nktv2p;
vector[3] = (ke_tensor[3] + virial[3]) * inv_volume * nktv2p;
vector[2] = vector[4] = vector[5] = 0.0;
} else {
vector[0] = virial[0] * inv_volume * nktv2p;
vector[1] = virial[1] * inv_volume * nktv2p;
vector[3] = virial[3] * inv_volume * nktv2p;
vector[2] = vector[4] = vector[5] = 0.0;
}
}
}

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