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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@13618 f3b2605a-c512-4ea7-a41b-209d697bcdaa

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This commit is contained in:
sjplimp
2015-07-16 22:34:54 +00:00
parent 6a79311dfc
commit a2c475b1a2
3 changed files with 68 additions and 8 deletions
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70
src/fix_momentum.cpp
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@ -36,7 +36,7 @@ FixMomentum::FixMomentum(LAMMPS *lmp, int narg, char **arg) :
nevery = force->inumeric(FLERR,arg[3]);
if (nevery <= 0) error->all(FLERR,"Illegal fix momentum command");
linear = angular = 0;
linear = angular = rescale = 0;
int iarg = 4;
while (iarg < narg) {
@ -50,6 +50,9 @@ FixMomentum::FixMomentum(LAMMPS *lmp, int narg, char **arg) :
} else if (strcmp(arg[iarg],"angular") == 0) {
angular = 1;
iarg += 1;
} else if (strcmp(arg[iarg],"rescale") == 0) {
rescale = 1;
iarg += 1;
} else error->all(FLERR,"Illegal fix momentum command");
}
@ -87,6 +90,35 @@ void FixMomentum::init()
void FixMomentum::end_of_step()
{
double **v = atom->v;
int *mask = atom->mask;
const int nlocal = atom->nlocal;
double ekin_old,ekin_new;
ekin_old = ekin_new = 0.0;
// compute kinetic energy before momentum removal, if needed
if (rescale) {
double *rmass = atom->rmass;
double *mass = atom->mass;
int *type = atom->type;
double ke=0.0;
if (rmass) {
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit)
ke += rmass[i] *
(v[i][0]*v[i][0] + v[i][1]*v[i][1] + v[i][2]*v[i][2]);
} else {
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit)
ke += mass[type[i]] *
(v[i][0]*v[i][0] + v[i][1]*v[i][1] + v[i][2]*v[i][2]);
}
MPI_Allreduce(&ke,&ekin_old,1,MPI_DOUBLE,MPI_SUM,world);
}
if (linear) {
double vcm[3];
group->vcm(igroup,masstotal,vcm);
@ -94,10 +126,6 @@ void FixMomentum::end_of_step()
// adjust velocities by vcm to zero linear momentum
// only adjust a component if flag is set
double **v = atom->v;
int *mask = atom->mask;
int nlocal = atom->nlocal;
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
if (xflag) v[i][0] -= vcm[0];
@ -137,4 +165,36 @@ void FixMomentum::end_of_step()
v[i][2] -= omega[0]*dy - omega[1]*dx;
}
}
// compute kinetic energy after momentum removal, if needed
if (rescale) {
double ke=0.0, factor=1.0;
double *rmass = atom->rmass;
double *mass = atom->mass;
int *type = atom->type;
if (rmass) {
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit)
ke += rmass[i] *
(v[i][0]*v[i][0] + v[i][1]*v[i][1] + v[i][2]*v[i][2]);
} else {
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit)
ke += mass[type[i]] *
(v[i][0]*v[i][0] + v[i][1]*v[i][1] + v[i][2]*v[i][2]);
}
MPI_Allreduce(&ke,&ekin_new,1,MPI_DOUBLE,MPI_SUM,world);
if (ekin_new != 0.0) factor = sqrt(ekin_old/ekin_new);
for (int i = 0; i < nlocal; i++) {
if (mask[i] & groupbit) {
v[i][0] *= factor;
v[i][1] *= factor;
v[i][2] *= factor;
}
}
}
}