[gmx-users] Bad energy conservation.

[Anton Feenstra]

Ram'on Garc'ia Fern'andez wrote:
> 
> On Wed, Dec 04, 2002 at 07:57:02PM +0100, David wrote:
> > if rlist < rcoul or rlist < rvdw, then a twin range setup is used, where
> > long range forces (rlist < r < rvdw) are only computed when you do
> > neighboursearching.
> 
> However, after hacking grompp so that it allows rlist > rvdw, I see
> that increasing rvdw has no effect on the LJ energy.
> 
> What is the meaning of rlist when rlist > rvdw?
> Does the interpretation of rlist depend on whether vdwtype = shift instead
> of vdwtype = cut-off?

Not to my knowledge. 
rlist is the distance for inclusion in the neighborlist, and the
corresponding interactions, that are outside rvdw/rcoul will be 
calculated each nstlist steps.

The reason grompp doesn't allow rlist > rvwd, is that it "doesn't 
make sense": you can set rvdw=rlist at no additional cost. However,
for testing purposes, or for 'special' systems (i.e. other than those
the developers happen to use), it might be desirable to be allowed
more freedom in choosing the r* parameters.


-- 
Groetjes,

Anton
 ________ ___________________________________________________________
|        | Anton Feenstra                                            |
| .      | Dept. of Pharmacochemistry - Vrije Universiteit Amsterdam |
| |----  | De Boelelaan 1083 - 1081 HV Amsterdam - The Netherlands   |
| |----  | Tel: +31 20 44 47608 - Fax: +31 20 44 47610               |
| ' __   | Feenstra at chem.vu.nl - http://www.chem.vu.nl/afdelingen/FAR|
|  /  \  |-----------------------------------------------------------|
| (    ) | Dept. of Biophysical Chemistry - University of Groningen  |
|  \__/  | Nijenborgh 4 - 9747 AG Groningen - The Netherlands        |
|   __   | Tel +31 50 363 4327 - Fax +31 50 363 4800                 |
|  /  \  | K.A.Feenstra at chem.rug.nl - http://md.chem.rug.nl/~anton   |
| (    ) |-----------------------------------------------------------|
|  \__/  | "Jesus Can't Save You, Though It's Nice to Think He Tried"|
|        | (Black Crowes)                                            |
|________|__