[gmx-users] adding new ion within the oplsaa force field

[Jose Borreguero]

Dear Gromacs users,

I'm trying to add a new type of atom as an ion. Looking at already existing
ions, such as sodium (NA), I see there's an entry both in files ions.itp
and aminoacids.rtp. My question is, what is the rationale of declaring ions
both as ions and as residues? Is this always required?

Best,
Jose Borreguero