compute rdf with expression for j-type in i-j pair?

Dear LAMMPS-users,

I would like to compute the rdf for an i-j pair where there are four atom types in the group-ID on the interval [n,m]; i is not equal to n or m; and the rdf excludes the i-i self-interaction.

I've searched the manual and mailing list and understand the use of the * wildcard for specifying i and j types (it works for all my other compute rdfs), but one of the compute group IDs has types 3, 4, 6, 9, & 10 and I would like the rdf for the [9 and (!= 9)] pair or the [9 and (*6 10)] pair or some other logical variant. Can the i- or j-type be specified as an expression/ non-continuous interval? The mail archive indicates that it can't be specified as a group.

I've completed the equilibration steps for the simulation and would like to avoid cracking open the data files and re-numbering the atom types for this one RDF. The simulation cells are triclinic, so I can't use VMD's RDF extension for any of this analysis (vmd > ...(ERROR) measure gofr: only orthorhombic cells are supported (for now)…). Is there a way to integrate this rdf into the LAMMPS simulations or will I have to post-process the dump files?

Thank you,


I don't understand the details of what you want to calculate, but
it sounds like compute rdf will not do the precise pairs you want.
So you have 3 choices:

a) suggest a modification to the input syntax of compute rdf that
    will allow specification of what you want
b) modify the code to compute rdf to do it (you have the source code)
c) post-process