[gmx-users] re: RB dihedral potential query in OPLS

chris.neale at utoronto.ca chris.neale at utoronto.ca
Thu Sep 14 01:16:27 CEST 2006

>"When using OPLS-AA force field for simulation in GROMACS,it's correct  to
>get a 14 energy term (Scaled) in  addition to the RB potential".

It is correct to get the 14 energy term in addition to the RB potential. The 14
energy term will be affected by FudgeLJ/QQ if you use the 0.5/0.5 gen-pairs=yes
as is intended for OPLS-AA... is this what you meant by "(scaled)"?.

>Ok so if that's the case can you please tell me in which case should i
>actually expect exclusion of the 14 interaction term when using RB

you should expect exclusion of 14 interaction terms when the RB potentials are
parameterized for the removal of 14 interaction terms. This is probably limited
to RB potentials in hydrocarbon chains (see references below). However, you must
read the papers that published the parameters that you are using for the real
answer to that question.

Ryckaert and Bellemans. 1975 Molecular dynamics of liquid n-butane near its
bioling point. Chem. Phys. Lett. 30:123-5

Ryckaert and Bellemans. 1978 Molecular dynamics of liquid alkanes. Faraday
Discuss. Chem. Soc. 66:95-106

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