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fix_wall.cpp
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Thu, Aug 22, 18:24

fix_wall.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.h"
#include "atom.h"
#include "domain.h"
#include "lattice.h"
#include "update.h"
#include "output.h"
#include "respa.h"
#include "error.h"
using namespace LAMMPS_NS;
enum{XLO,XHI,YLO,YHI,ZLO,ZHI};
/* ---------------------------------------------------------------------- */
FixWall::FixWall(LAMMPS *lmp, int narg, char **arg) :
Fix(lmp, narg, arg)
{
scalar_flag = 1;
vector_flag = 1;
size_vector = 6;
global_freq = 1;
extscalar = 1;
extvector = 1;
time_depend = 1;
// parse args
for (int m = 0; m < 6; m++) wallflag[m] = 0;
velflag = 0;
wigflag = 0;
int scaleflag = 1;
int iarg = 3;
while (iarg < narg) {
if ((strcmp(arg[iarg],"xlo") == 0) || (strcmp(arg[iarg],"xhi") == 0) ||
(strcmp(arg[iarg],"ylo") == 0) || (strcmp(arg[iarg],"yhi") == 0) ||
(strcmp(arg[iarg],"zlo") == 0) || (strcmp(arg[iarg],"zhi") == 0)) {
if (iarg+5 > narg) error->all("Illegal fix wall command");
int m;
if (strcmp(arg[iarg],"xlo") == 0) m = XLO;
else if (strcmp(arg[iarg],"xhi") == 0) m = XHI;
else if (strcmp(arg[iarg],"ylo") == 0) m = YLO;
else if (strcmp(arg[iarg],"yhi") == 0) m = YHI;
else if (strcmp(arg[iarg],"zlo") == 0) m = ZLO;
else if (strcmp(arg[iarg],"zhi") == 0) m = ZHI;
wallflag[m] = 1;
coord0[m] = atof(arg[iarg+1]);
epsilon[m] = atof(arg[iarg+2]);
sigma[m] = atof(arg[iarg+3]);
cutoff[m] = atof(arg[iarg+4]);
iarg += 5;
} else if (strcmp(arg[iarg],"vel") == 0) {
if (iarg+2 > narg) error->all("Illegal fix wall command");
velflag = 1;
double vtmp = atof(arg[iarg+1]);
for (int m = 0; m < 6; m++) vel[m] = vtmp;
iarg += 2;
} else if (strcmp(arg[iarg],"wiggle/sin") == 0) {
if (iarg+3 > narg) error->all("Illegal fix wall command");
wigflag = 1;
double atmp = atof(arg[iarg+1]);
period = atof(arg[iarg+2]);
for (int m = 0; m < 6; m++) amplitude[m] = atmp;
iarg += 3;
} else if (strcmp(arg[iarg],"wiggle/cos") == 0) {
if (iarg+3 > narg) error->all("Illegal fix wall command");
wigflag = 2;
double atmp = atof(arg[iarg+1]);
period = atof(arg[iarg+2]);
for (int m = 0; m < 6; m++) amplitude[m] = atmp;
iarg += 3;
} else if (strcmp(arg[iarg],"units") == 0) {
if (iarg+2 > narg) error->all("Illegal fix wall command");
if (strcmp(arg[iarg+1],"box") == 0) scaleflag = 0;
else if (strcmp(arg[iarg+1],"lattice") == 0) scaleflag = 1;
else error->all("Illegal fix wall command");
iarg += 2;
} else error->all("Illegal fix wall command");
}
// error check
int flag = 0;
for (int m = 0; m < 6; m++) if (wallflag[m]) flag = 1;
if (!flag) error->all("Illegal fix wall command");
for (int m = 0; m < 6; m++)
if (wallflag[m] && cutoff[m] <= 0.0)
error->all("Fix wall cutoff <= 0.0");
if (velflag && wigflag)
error->all("Cannot set both vel and wiggle in fix wall command");
if ((wallflag[XLO] || wallflag[XHI]) && domain->xperiodic)
error->all("Cannot use fix wall in periodic dimension");
if ((wallflag[YLO] || wallflag[YHI]) && domain->yperiodic)
error->all("Cannot use fix wall in periodic dimension");
if ((wallflag[ZLO] || wallflag[ZHI]) && domain->zperiodic)
error->all("Cannot use fix wall in periodic dimension");
if ((wallflag[ZLO] || wallflag[ZHI]) && domain->dimension == 2)
error->all("Cannot use fix wall zlo/zhi for a 2d simulation");
// setup scaling
if (scaleflag && domain->lattice == NULL)
error->all("Use of fix wall with undefined lattice");
double xscale,yscale,zscale;
if (scaleflag) {
xscale = domain->lattice->xlattice;
yscale = domain->lattice->ylattice;
zscale = domain->lattice->zlattice;
}
else xscale = yscale = zscale = 1.0;
// apply scaling factors to coord0, vel, amplitude
double scale;
for (int m = 0; m < 6; m++) {
if (wallflag[m] == 0) continue;
if (m < 2) scale = xscale;
else if (m < 4) scale = yscale;
else scale = zscale;
coord0[m] *= scale;
if (velflag) vel[m] *= scale;
if (wigflag) amplitude[m] *= scale;
}
// setup oscillations
if (wigflag) {
double PI = 4.0 * atan(1.0);
omega = 2.0*PI / period;
}
eflag = 0;
for (int m = 0; m < 7; m++) ewall[m] = 0.0;
time_origin = update->ntimestep;
}
/* ---------------------------------------------------------------------- */
int FixWall::setmask()
{
int mask = 0;
mask |= POST_FORCE;
mask |= THERMO_ENERGY;
mask |= POST_FORCE_RESPA;
mask |= MIN_POST_FORCE;
return mask;
}
/* ---------------------------------------------------------------------- */
void FixWall::init()
{
dt = update->dt;
// setup coefficients
for (int m = 0; m < 6; m++)
if (wallflag[m]) precompute(m);
if (strcmp(update->integrate_style,"respa") == 0)
nlevels_respa = ((Respa *) update->integrate)->nlevels;
}
/* ---------------------------------------------------------------------- */
void FixWall::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);
}
}
/* ---------------------------------------------------------------------- */
void FixWall::min_setup(int vflag)
{
post_force(vflag);
}
/* ---------------------------------------------------------------------- */
void FixWall::post_force(int vflag)
{
eflag = 0;
for (int m = 0; m < 7; m++) ewall[m] = 0.0;
// coord0 = initial position of wall
// coord = current position of wall
double delta = (update->ntimestep - time_origin) * dt;
double coord;
for (int m = 0; m < 6; m++) {
if (wallflag[m] == 0) continue;
if (velflag) {
if (m % 2 == 0) coord = coord0[m] + delta*vel[m];
else coord = coord0[m] - delta*vel[m];
} else if (wigflag == 1) {
if (m % 2 == 0) coord = coord0[m] + amplitude[m]*sin(omega*delta);
else coord = coord0[m] - amplitude[m]*sin(omega*delta);
} else if (wigflag == 2) {
if (m % 2 == 0) coord = coord0[m] + amplitude[m]*(1.0-cos(omega*delta));
else coord = coord0[m] - amplitude[m]*(1.0-cos(omega*delta));
} else coord = coord0[m];
wall_particle(m,coord);
}
}
/* ---------------------------------------------------------------------- */
void FixWall::post_force_respa(int vflag, int ilevel, int iloop)
{
if (ilevel == nlevels_respa-1) post_force(vflag);
}
/* ---------------------------------------------------------------------- */
void FixWall::min_post_force(int vflag)
{
post_force(vflag);
}
/* ----------------------------------------------------------------------
energy of wall interaction
------------------------------------------------------------------------- */
double FixWall::compute_scalar()
{
// only sum across procs one time
if (eflag == 0) {
MPI_Allreduce(ewall,ewall_all,7,MPI_DOUBLE,MPI_SUM,world);
eflag = 1;
}
return ewall_all[0];
}
/* ----------------------------------------------------------------------
components of force on wall
------------------------------------------------------------------------- */
double FixWall::compute_vector(int n)
{
// only sum across procs one time
if (eflag == 0) {
MPI_Allreduce(ewall,ewall_all,7,MPI_DOUBLE,MPI_SUM,world);
eflag = 1;
}
return ewall_all[n+1];
}

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