dynamic groups in LAMMPS

Hi all - we just added an option to the group command to make groups dynamic,
meaning that which atoms are in the group can be determined

periodically on-the-fly during a simulation.

Thanks to Axel and Aidan for suggesting useful options for how it

should work. A region and/or atom-style variable can be used
to flag which atoms belong to the group.

This is a feature people have asked about from time to time.

Please use with caution. As Aidan said, this opens up a whole

new set of possible ways to run unphysical simulations.


I was just attempting to have a play with this, and I'm getting the error "ERROR: Invalid fix style."

It looks like group is trying to create a fix of type GROUP, but that doesn't seem to be present (not listed in the lmp -help output, and no fix_group.cpp). This is from revision 11494. Has anybody else had the same problem?

The commands I've used:

lattice sc 0.4
region box block 0 5 0 5 0 20
create_box 1 box
create_atoms 1 box

region ht_right block INF INF INF INF 19 20
group hotreg dynamic all region ht_right every 1


probably forgot to check in the new fix_group.cpp file -
will check later this AM and post an updated patch