This is somewhat in regard to my previous post about using fix/rigid
with a massless site: http://lammps.sandia.gov/threads/msg15547.html
Since the massless site was my COM and this is what I was wanting, I
dumped only this massless site to a custom xyz file.
dump 1 com custom 500 test.xyz id xu yu zu
where "com" was just this massless site.
The resulting trajectory seems to have the coordinates wrapped instead
of unwrapped about the PBC as I expected.
I was using the October 3, 2010 source of Lammps.
Does this have to do with dumping part of a rigid molecule or something?
Sorry if I missed it in the manual.