[gmx-users] Why density increase with increasing the cutoff length?

[David van der Spoel]

On 12/21/09 5:32 PM, Yanmei Song wrote:
> Thanks for all the helpful response. But do I have to use dispersion
> correction when I use PME? I don't quite understand what dispersion
> correction do. Sometime I found using dispersion correction make my
> results worse for a large molecule system.

Read the manual please.

>
> On Mon, Dec 21, 2009 at 12:48 AM, David van der Spoel
> <spoel at xray.bmc.uu.se <mailto:spoel at xray.bmc.uu.se>> wrote:
>
>     On 12/21/09 8:03 AM, Yanmei Song wrote:
>
>         Dear Users:
>
>         Anyone can explain why the density of the water models increase with
>         increase the cutoff length. I tried a couple water models in
>         reaction-field, PME simulations.The cutoff length ranged from 0.9 to
>         1.5. They all show the same trend. Then there must be some reasons.
>         Anyone can tell me why?
>
>         --
>         Yanmei Song
>         Ph.D. Candidate
>         Department of Chemical Engineering
>         Arizona State University
>
>     Van der Waals interactions. I guess you have not turned on the
>     dispersion correction. If you do the effect should be far less.
>
>     --
>     David van der Spoel, Ph.D., Professor of Biology
>     Molec. Biophys. group, Dept. of Cell & Molec. Biol., Uppsala University.
>     Box 596, 75124 Uppsala, Sweden. Phone:  +46184714205. Fax: +4618511755.
>     spoel at xray.bmc.uu.se <mailto:spoel at xray.bmc.uu.se> spoel at gromacs.org
>     <mailto:spoel at gromacs.org> http://folding.bmc.uu.se
>     --
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>
>
>
> --
> Yanmei Song
> Ph.D. Candidate
> Department of Chemical Engineering
> Arizona State University
>


-- 
David.
________________________________________________________________________
David van der Spoel, PhD, Professor of Biology
Dept. of Cell and Molecular Biology, Uppsala University.
Husargatan 3, Box 596,  	75124 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://folding.bmc.uu.se
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