[gmx-users] unit conversion

[Hyunjin Kim]

Hi,

When I convert FF parameters from OPLS (in Gromacs) to Charmm, I divide
bond and angle force constants, i.e., Kb and Ktheta, by 836.8 and 8.368.
However, parameters for tip3p water do not convert properly in this ways.

For example, Kb = 502416.0 kJ/mol/nm^2 for OW-HW in Gromacs and 450.0
kcal/mol/A^2 in Charmm.
502416.0/836.8 = 600.4 instead of 450.0.

I wonder what I did is incorrect.

Thanks.

Hyunjin.