Dear Prof. Dubbeldam,

I am trying to implement the force field with the torsion potential for a molecule which includes a non-zero phase angle term f to account for asymmetric rotational barriers:

U = C_0 + C1[1 + cos(phi +f) ] + C2[1-cos(2(phi + f)] + C3[1-cos(3(phi + f)]

and could not find the proper form in the manual.

Is there a way to implement this form of the potential in RASPA?

Thank you!