Dear Dr. Axel Kohlmeyer,

Hello Dr. Kohlmeyer. I deeply appreciate your many advices on my inquiries to LAMMPS.

I would like to ask a question on compute rdf in LAMMPS.

I have a system 100 atoms in my simulation box where I have 40 Type 1 atoms and 60 Type 2 atoms interacting via LJ potential.

I wanted to see how the Type 2 atoms are distributed with respect to Type 1 atoms. I named by Type 1 atoms as “PN” and my Type 2 atoms as “SN.” Therefore, I included the following command:

compute myRDF all rdf 200 1 2 cutoff 5.0

According to the documentation, if I specified “all” as the group-ID, then the radial distribution function will be normalized with the bulk density of the entire system.

However, when I specified the “PN” as the group-ID, I was curious if the bulk density will only consist of the Type 2 atoms as if the following:

compute myRDF PN rdf 200 1 2 cutoff 5.0_{}^{}

I compared my simulation result between using these two commands, and I obtained exact same RDF for the two cases, one that considers all atoms and other that considers only Type 1 atoms.

I was curious if there are ways to have the radial distribution function only compute the bulk density of the specific types of atoms desired. Thank you.

Sincerely,

Masato Koizumi

_{}^{}

compute 1 fluid rdf 500 1 1 1 2 2 1 2 2_{}^{}