Torsional potential with phase angle term

[ae213]

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!

[David Dubbeldam]

Depending on the value of 'f' you could probably rewrite that functional form into into another form that is supported (using cosine and sine rules). If that is not possible, another option is add the functional form in the code.