[gmx-users] Problem with coulombtype=user and 1,4 interactions
muecksch at rhrk.uni-kl.de
Sun Nov 28 01:06:41 CET 2010
Dear Gromacs experts,
I've been trying to use a tabulated potential for the
coulombic-interactions with all Gromacs versions from 4.0.7 to 4.5.3.
In combination with OPLS/AA force field and SPC/E water I used a
potential by Gezelter for a simple system consisting of a protein in
Fennell, Christopher J. ; Gezelter, J. D.: Is the Ewald summation still
necessary? Pairwise alternatives to the accepted standard for long–range
elec- trostatics. In: Journal of Chemical Physics 124 (2006)
When I run mdrun I specify sth. like this:
mdrun_mpi_s -table table_gezelter_s.xvg -tablep table_gezelter_s.xvg -v
My problem is that the 14 Coulomb-energy is approximately half the value
of that compared to PME-switch.
The Coulomb-SR energy is approximately at the same value as PME and
everything else works alright.
So there's sth. wrong with the 1,4 energies. Since OPLS/AA uses a
scaling factor of 1/2 for the 1,4-interactions changing it will mess up
the whole simulation since the 1,4 LJ energies will get wrong. If I use
another table for the 1,4 interactions multiplied by a factor of 2
everything gets worse.
As a consequence this potential fails to reproduce densities etc.
So what am I missing? Is it the potential that's wrong?
Thanks alot for any ideas!
Department of Physics
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Phone: +49 (0)631 205 4287
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Email: muecksch at rhrk.uni-kl.de
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