GROMACS modification: No
In the Amber force field port for the Gromacs, I find only one single epsilon/sigma parameters for the mono- and divalent ions/cations. I tried to track the origin of these parameters without any luck; they look neither like Joung-Cheatham nor the Aqvist ion parameters. Does anyone know anything about this?
Thank you all!
Edit: I have found the answer. Apparently these ion parameters are included in the parm99 files of Amber package and 1990 Amber-adapted Aqvist parameters. I leave this here in case someone comes up with the same question in the future. Sorry for the false alarm.