[lammps-users] About the use of OPLS improper parameters


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.

Thank you,

LAMMPS allows to select the functional form for each part of the total potential individually. Therefore there does not have to be an “opls” improper style, if the same functional form is provided by an existing improper style. So to find if there is a fit, you have to review the existing styles and compare them to the potential function in the OPLS/AA publication(s).


Hi Manish,

This website can be useful: http://zarbi.chem.yale.edu/ligpargen/
We have used cvff style for OPLS improper in LAMMPS


Thank you, Ivan. I will check it out.