[jusy1]

I am trying to simulate oxygen using gromacs but there seems to be no forcefield parameters for this molecule.

So I would like to add a forcefield to gromacs which is a 3 site model: The two oxygens are lennard jones particles and there's a point charge at the center of mass.

The reference article is: "New force fields for nitrous oxide and oxygen and their application to phase equilibria simulations", Niels Hansen et al

I was wondering if there's anyone more proficient with gromacs that could indicate me how to do this (files to modify, how to represent the center of mass particle, etc)

Thank you