Torsion Angle with 5 parameters (Trappe)

Dear Cassandra-developer and Cassandra-User,

I want to simulate butadiene with the Trappe force-field.
Dihedral interaction is described by the following function:

u = c0 + c1 cos(a) + c2 cos(2a) + c3 cos(3a) + c4 cos(4a)

Can Cassandra handle five parameters, if I use OPLS-form?

Thank you very much in advance

Mark

It looks like it might not be too difficult, but I might be missing some things and the developers can comment more.

1) You would have to change input_routines.f90, in the Get_Dihedral_Info subroutine, where it reads in the OPLS parameters. You'd have to change this to read in 5 parameters

2) Then in energy_routines.f90 you'd have to change the Compute_Molecule_Dihedral_Energy subroutine to change the assigning of the parameters to add an "a4" and then change the edihed to include the a4 term.

Josh

Dear Josh,

thanks a lot for your advice. I will try it and will tell you.

Mark