[gmx-users] Re: DMSO G53a6 FF in Gromacs

[Berk Hess]

> Date: Wed, 12 Mar 2008 17:20:19 +0100
> From: andreas.frank at ch.tum.de
> To: gmx-users at gromacs.org
> Subject: Re: [gmx-users] Re: DMSO G53a6 FF in Gromacs
> 
> Dear all,
> 
> I think I found the reason for the deviation after "hunderds of small 
> runs"...:-): I normally used Dispersion Correction for both the energy 
> and pressure because in the manual the following is noted:
> 
> "...The pressure correction in contrast is very large and can not be 
> neglected. Although it is in principle possible to
> parameterize a force field such that the pressure is close to 1 bar even 
> without correction, such a method makes
> the parameterization dependent on the cut-off and is therefore 
> undesirable. Please note that it is not consistent to
> use the long range correction to the dispersion without using either a 
> reaction field method or a proper long range
> electrostatics method such as Ewald summation or PPPM."
> 
> Maybe I got it wrong (and I am still a little bit confused) but because 
> I used the reaction-field approximation I turned on DispCorr for 
> Pressure. However, it seems that the Gromos DMSO FF was established in a 
> way that the correction is "included" in the parameter set which was / 
> is not clear to me when reading the DMSO paper.

Reaction-field is for electrostatics and has nothing to do with dispersion correction,
which is for Van der Waals interactions.

Gromos force fields never use a dispersion correction.

Berk.


_________________________________________________________________
Express yourself instantly with MSN Messenger! Download today it's FREE!
http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://maillist.sys.kth.se/pipermail/gromacs.org_gmx-users/attachments/20080312/13528e81/attachment.html>