CHARMM Development Project Forums User Discussion & Questions Energy terms, Constraints, Restraints, and Solvation Protein center of mass and urea rdf

COOR ANAL is mostly intended for solvent analysis.

I don't think COOR ANAL is doing what you want here; you probably need to use an atom close to the center of mass of each molecule as a surrogate to get something that approximates your goal.

Also, you probably want ISDIST instead of IGDIST.