[gmx-users] Charge derrivation for OPLSAA forcefield

[Dommert Florian]

On Tue, 2012-05-08 at 11:38 -0700, Milinda Samaraweera wrote: 
> Hi Guys
> 
> 
> I was using the program http://q4md-forcefieldtools.org/RED/ to
> derrive ESP based charges for some molecules that I study. Is this a
> correct method to do so if not please let me know what are the other
> methods that are available.
> 

Hi,

this is really a hard questions to answer. Different methods to derive
partial charges are present, which rely on various ideas. Actually, the
partial charges of a force field should be consistent, because they are
anyway just an approximation for the true charge density. Common force
fields like AMBER or OPLS-AA were constructed with different
consideration, giving rise to the differences, though they allow to
desribe the same molecules. So I would study, how the remaining
parameters of the applied force field were derived. Furthermore be aware
that altering a single charge of force field might require readaption of
dihedral and LJ parameters. Hence, always be careful and benchmark the
force field  against single as well collective static and dynamic
properties, carefully.

/Flo

> 
> thanks alot
>  
> Milinda Samaraweera
> University of Connecticut
> Department of Chemistry
> 55 N Eagleville road
> unit 3060
> Storrs CT
> USA
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-- 
Florian Dommert
Dipl. - Phys.

Institute for Computational Physics
University Stuttgart

Pfaffenwaldring 27
70569 Stuttgart

EMail: dommert at icp.uni-stuttgart.de
Homepage: http://www.icp.uni-stuttgart.de/~icp/Florian_Dommert

Tel.: +49 - (0)711 - 68563613
Fax.: +49 - (0)711 - 68563658
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