I am trying to simulate an ionic liquid in LAMMPS. I have set all forcefield parameters except for improper torsion. I want to use the OPLS parameters given in the literature (in V1 V2 V3… format), but I do not know how to use them in the Lammps. Since there is no OPLS improper style in Lammps, I can not use those improper parameters as it is. Please tell me if there is any way of using this? Do I have to convert these parameters in some other improper style like Cvff or Harmonic? In that case, what would be the conversion factor?
Any help would be appreciated.