[gmx-users] OPLS-AA Coulomb-14 energies incorrect?

Malcolm Gillies malcolm.b.gillies at anu.edu.au
Wed Aug 6 09:57:01 CEST 2003

On Wed, 2003-08-06 at 17:23, Erik Lindahl wrote:
> First - I think I know what the cause of the difference might be. By 
> default, the pdb2gmx program does not generate 1,4 interactions for 
> hydrogens since that's the prescribed setup for the other force fields. 
>   Use the -H14 flag for pdb2gmx to get the OPLS-AA standard.

Thanks, with the -H14 flag, the Coulomb energies now agree to within a
fraction of a percent.

> This will probably be the default in future Gromacs versions (it's 
> already changed in CVS), but we would probably confuse users more by 
> changing the default in a point release....

Right, perhaps a warning in the header of the ffoplsaa.itp file might be
in order, if it's not a default for pdb2gmx.

> I've just uploaded a tarball with 
> the latest OPLS parameters to the contrib section of www.gromacs.org if 
> you want to play with it.

Great, thanks!


Malcolm Gillies <Malcolm.B.Gillies at anu.edu.au>
Postdoctoral Fellow, Computational Proteomics and Therapy Design Group,
John Curtin School of Medical Research, Australian National University

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