[gmx-users] How to convert C6&C12 from GROMOS54a7 to sigma&epsilon for OPLSAA

[Ming Tang]

Dear all,

I want to calculate sigma&epsilon for OPLSAA.ff from C6&C12 developed based on GROMOS54a7.ff.

>From the manual, I got the equations:



C12 = Sigma^(6)*C6
C6 = 4*sigma^(6)*epsilon
However, I found sigma and epsilon are different in OPLSAA and AMBER, and that C6&C12 from GROMOS and sigma&epsilon from OPLSAA do not match these equations. Could anybody give me some guidance?

Thanks,
Ming