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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@431 f3b2605a-c512-4ea7-a41b-209d697bcdaa

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sjplimp
2007-03-22 17:05:51 +00:00
parent 2f25e80bf2
commit 9926a91608
4 changed files with 40 additions and 1 deletions
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25
src/group.cpp
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@ -646,6 +646,31 @@ void Group::vcm(int igroup, double masstotal, double *cm)
cm[2] /= masstotal;
}
/* ----------------------------------------------------------------------
compute the total force on group of atoms
------------------------------------------------------------------------- */
void Group::fcm(int igroup, double *cm)
{
int groupbit = bitmask[igroup];
double **f = atom->f;
int *mask = atom->mask;
int nlocal = atom->nlocal;
double flocal[3];
flocal[0] = flocal[1] = flocal[2] = 0.0;
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
flocal[0] += f[i][0];
flocal[1] += f[i][1];
flocal[2] += f[i][2];
}
MPI_Allreduce(flocal,cm,3,MPI_DOUBLE,MPI_SUM,world);
}
/* ----------------------------------------------------------------------
compute the radius-of-gyration of group around center-of-mass cm
must unwrap atoms to compute Rg correctly