I’m using the group dynamic command. Is it possible to allow dynamic group’s parent group to be a certain “type” of atoms or a dynamic group? Because, for grand canonical Monte Carlo (GCMC) simulations, there are inserting/deleting operations. For an ensemble with more than one type of atoms, if we assign some regions, their parent group is a dynamic group. So, allowing a dynamic parent group or having “type” keyword for dynamic group may solve this problem and make it easier to use for GCMC simulations.
You can define a group to mean atoms of a certain type, with the group
command. Commands that add atoms, like fix pour, typically
have an option to specify a group that new atoms will be added to
(see the fix pour doc page). I don’t know if fix gcmc does that (Paul
can answer). If it does, then using that group=type group as the parent group
for a dynamic group you define, will do what you want.
For fix GCMC, exchanged atoms/molecules are assigned to two groups: the default group “all” and the group specified in the fix gcmc command (which can also be “all”). When using the atom option in fix GCMC, all inserted atoms are also of the user-specified type. But when the molecule option is used, the inserted atoms can be of different types. Fix GCMC and fix pour are similar in this regard.
I added a sentence to the fix gcmc doc page to clarify this.