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fix_wall_lj93.cpp
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Sat, Sep 14, 16:21

fix_wall_lj93.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 "math.h"
#include "stdlib.h"
#include "string.h"
#include "fix_wall_lj93.h"
#include "atom.h"
#include "update.h"
#include "output.h"
#include "respa.h"
#include "error.h"
using namespace LAMMPS_NS;
/* ---------------------------------------------------------------------- */
FixWallLJ93::FixWallLJ93(LAMMPS *lmp, int narg, char **arg) :
Fix(lmp, narg, arg)
{
if (narg != 8) error->all("Illegal fix wall/lj93 command");
if (strcmp(arg[3],"xlo") == 0) {
dim = 0;
side = -1;
} else if (strcmp(arg[3],"xhi") == 0) {
dim = 0;
side = 1;
} else if (strcmp(arg[3],"ylo") == 0) {
dim = 1;
side = -1;
} else if (strcmp(arg[3],"yhi") == 0) {
dim = 1;
side = 1;
} else if (strcmp(arg[3],"zlo") == 0) {
dim = 2;
side = -1;
} else if (strcmp(arg[3],"zhi") == 0) {
dim = 2;
side = 1;
} else error->all("Illegal fix wall/lj93 command");
coord = atof(arg[4]);
epsilon = atof(arg[5]);
sigma = atof(arg[6]);
cutoff = atof(arg[7]);
coeff1 = 6.0/5.0 * epsilon * pow(sigma,9.0);
coeff2 = 3.0 * epsilon * pow(sigma,3.0);
coeff3 = 2.0/15.0 * epsilon * pow(sigma,9.0);
coeff4 = epsilon * pow(sigma,3.0);
double rinv = 1.0/cutoff;
double r2inv = rinv*rinv;
double r4inv = r2inv*r2inv;
offset = coeff3*r4inv*r4inv*rinv - coeff4*r2inv*rinv;
}
/* ---------------------------------------------------------------------- */
int FixWallLJ93::setmask()
{
int mask = 0;
mask |= POST_FORCE;
mask |= THERMO_ENERGY;
mask |= POST_FORCE_RESPA;
mask |= MIN_POST_FORCE;
return mask;
}
/* ---------------------------------------------------------------------- */
void FixWallLJ93::init()
{
if (strcmp(update->integrate_style,"respa") == 0)
nlevels_respa = ((Respa *) update->integrate)->nlevels;
}
/* ---------------------------------------------------------------------- */
void FixWallLJ93::setup()
{
eflag_enable = 1;
if (strcmp(update->integrate_style,"verlet") == 0)
post_force(1);
else {
((Respa *) update->integrate)->copy_flevel_f(nlevels_respa-1);
post_force_respa(1,nlevels_respa-1,0);
((Respa *) update->integrate)->copy_f_flevel(nlevels_respa-1);
}
eflag_enable = 0;
}
/* ---------------------------------------------------------------------- */
void FixWallLJ93::min_setup()
{
eflag_enable = 1;
post_force(1);
}
/* ---------------------------------------------------------------------- */
void FixWallLJ93::post_force(int vflag)
{
bool eflag = false;
if (eflag_enable) eflag = true;
else if (output->next_thermo == update->ntimestep) eflag = true;
double **x = atom->x;
double **f = atom->f;
int *mask = atom->mask;
int nlocal = atom->nlocal;
double delta,rinv,r2inv,r4inv,r10inv,eng;
if (eflag) eng = 0.0;
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
if (side == -1) delta = x[i][dim] - coord;
else delta = coord - x[i][dim];
if (delta <= 0.0) continue;
if (delta > cutoff) continue;
rinv = 1.0/delta;
r2inv = rinv*rinv;
r4inv = r2inv*r2inv;
r10inv = r4inv*r4inv*r2inv;
f[i][dim] -= (coeff1*r10inv - coeff2*r4inv) * side;
if (eflag) eng += coeff3*r4inv*r4inv*rinv - coeff4*r2inv*rinv - offset;
}
if (eflag) MPI_Allreduce(&eng,&etotal,1,MPI_DOUBLE,MPI_SUM,world);
}
/* ---------------------------------------------------------------------- */
void FixWallLJ93::post_force_respa(int vflag, int ilevel, int iloop)
{
if (ilevel == nlevels_respa-1) post_force(vflag);
}
/* ---------------------------------------------------------------------- */
void FixWallLJ93::min_post_force(int vflag)
{
post_force(vflag);
}
/* ---------------------------------------------------------------------- */
double FixWallLJ93::thermo(int n)
{
if (n == 0) return etotal;
else return 0.0;
}

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