Is it possible to use the opls force field in GULP? It seems that all the parts are present except for the form of dihedral contribution in the opls format.
Could we have a torsional form incorporated in GULP corresponding to opls? Although it seems like it can be constructed from the standard torsional potential available k(1+cos(n phi - phi0)), the preparation of the input file would be more difficult this way.
You are correct, in that should be straightforward to use the OPLS force field in GULP & this has certainly been done in the past. Iām not quite sure what the issue is for the torsion term though, since GULP has the same functional form as OPLS - you just have to divide the k value by 2 to allow for the half in the OPLS form. GULP allows layering of force fields (i.e. you can add as many different terms and potentials together if there is no clash in formalism), which means you just need to copy and paste the torsion to create the multiple values of n with different k values.
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