I have noticed a discrepancy in the msi2lmp converter. Specifically, it seems that the dihedral energy constant (K) that is read in from cvff.frc (or other biosym files) is getting reduced by a factor of 4 in the lammps data file. Here is an example using benzene:
From cvff.frc, showing K = 12.0 kcal/mol:
#torsion_1 cvff
E = Kphi * [ 1 + cos(n*Phi - Phi0) ]
!Ver Ref I J K L Kphi n Phi0
!---- — ---- ---- ---- ---- ------- ------ -------
1.0 1 * cp cp * 12.0000 2 180.0000
and from the lammps data file showing K = 3.0 kcal/mol:
Dihedral Coeffs
1 3.0000 -1.0000 2.0000
I am not an expert at C, and have not been able to identify where this conversion is made in the code. I would like to know if I am missing something in the conversion.
Thanks,
Jeff Greathouse