[gmx-developers] triplet range cut-off

David van der Spoel spoel at xray.bmc.uu.se
Thu Sep 6 16:03:33 CEST 2007

marcos wrote:
> Hello,
> We are simulating liquid-gas interfaces and we want to include the long
> range forces due to VDW during the course of the simulation. 
> We think to implement a kind of triplet range cut-off. This is to add a
> new (and longer) cut-off to the already existent in the twin-range
> method. This new cut-off will be very long and the forces will be
> updated very infrequently. 
> We plan to apply this only to the VDW interaction, whereas the
> electrostatics will be handled with PME.
> Another possibility is to use a VDW analog of the PME but update the
> forces very rarely.
> Which option do you like more, and where would be the place to start
> modifying the code?
The PME-Van der Waals would be nice to have as an option.

However, for your problem you might consider whether you shouldn't 
rather have an analytical approximation: the gas will feel the liquid a 
lot more than the other way around, but you could have some kind of 
Z-dependent force due to dispersion (if Z is perpendicular to the 
interface). You should in that case also consider the Wall potentials 
that Berk implemented in the CVS branch.

David van der Spoel, Ph.D.
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	spoel at gromacs.org   http://folding.bmc.uu.se

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