Add missing residue in rtp in gromos54 a7 force field

GROMACS version: gromacs 2018.7
GROMACS modification: Yes/No
Here post your question : I am trying to perform protein ligand MD simulation, where I have used ATB for creating ligand topology. While “adding ion” step, it is showing CPos atom is not found, but it is present in ATP file of gromos 54-a7,not present in rtp file. So how to add this residue in rtp file ? please help me.

maybe you can find the answer to your problems by looking at the previuos post in this forum
see for example