potential energy per chain

I have a system made of multiple polymer chains around 100. Each chains is
made of 200 atoms. I know that the pe/chain can be computed using compute
pe/atom then summing pe of each atom in the chain. my problem is that my
system is mode 100 chains and lammps only allows for 23 groups to be created
and the compute/pe command is as follow “compute ID group-ID pe/atom keyword
…”. How Can i do it for more than 23 chains.

Version 1 of what Axel wrote is the way to do it
in current LAMMPS. Fix ave/chunk can sum
any per-atom property over the atoms in each chunk
(chunk = molecule in your case).

ideally, we would have a compute style reduce/chunk for that in
LAMMPS. i am currently working on that. i am surprised it hasn’t come
up before.

If you wanted the max PE in any chain, then the
variable command can do this, with functions like
max(), min(), sum(), ave(), using the output from fix ave/chunk
as the arguments of those functions. These are analogous
to what compute reduce does for per-atom data.

Compute reduce/chunk would do a per chunk reduction and not a reduction over chunks.

Axel

Thanks alot