new chunk commands

We released a patch today with several new “chunk” commands.

Chunks are defined as collections of atoms (molecules, spatial bins,

atoms with the same coordination #, etc), which you can define
in a variety of ways via compute chunk/atom. You can then sum per-atom
values by chunk. So this will replace fix ave/spatial (at some point
in the future) as a more general and flexible way to compute system properties

based on subsets of atoms.

This doc page gives a summary:

These are the new commands:

compute chunk/atom, fix ave/chunk

compute com/chunk
compute gyration/chunk
compute inertia/chunk
compute msd/chunk
compute property/chunk
compute temp/chunk
compute torque/chunk
compute vcm/chunk