[gmx-users] center of mass motion

[Erik Lindahl]

On Fri, 2001-11-09 at 11:38, Luca Monticelli wrote:
> 
> Dear all,
> 
> is there an EASY way to calculate the center of mass of a group of atoms
> as a function of time (and possibly print it out as a whatever.xvg file)?
> I found that the g_dist program calculates the distance between the
> centers of mass of two groups of atoms as a function of time, which is
> different from what I need. Anybody has suggestions?
> 
> Thanks a lot
> Luca

Hi Luca,

The g_traj program does this for you - just provide an index file with
the group(s) you want to calculate c.o.m. for and use the -com option.
There are a couple of other options too, you can e.g. choose to remove
jumps across the box due to pbc and have an index with molecule instead
of atom numbers.

Regards,

Erik