[lammps-users] Group command with specific variable

Dear steve,

I want to group some atoms (whose common neighbor analysis number = 5) with group command.

I compute them with compute cna command but can not group them with group command.

(According to the manual, group command can only deal with type, id or molecule. not cna)

Is there any other method in LAMMPS to dump atoms having certain number of CNA exclusively?

I currently use pizza.py as post-processor to achieve this but this takes long due to the large size of initial dump files)


The dump_modify thresh command lets you output atoms which
meet a specific criterion. Like their current CNA value is over
a certain value. Because CNA values change dynamically,
that is not really what groups are designed for in LAMMPS lingo.