Repulsive potential between virtual sites

GROMACS version: 2021.4
GROMACS modification: No

Dear gmx users,

System : Protein in water

In charmm36 and amber99sb-ildn, comb-rule = 2.

When setting up a repulsive potential between virtual sites, can I apply the same conversion of Rmin (1.2 nm) to sigma (1.06908) for both force fields,? Or, any other conversions required?

Thanks for your help.

The Rmin to sigma coversion is general for the Lennard-Jones potential and does not depend on the force field. But there might be unit conversions that depend on the force fields you convert between.