[gmx-users] dielectric constant

[David van der Spoel]

Mark Abraham wrote:
> gadies at fh.huji.ac.il wrote:
>>
>> Hello,
>>
>> I'm interested in running a simulation in which the box will be 
>> divided in to two different dielectric constants separated at a plane.
>> Is it possible to do that in Gromacs?
> 
> Possible, yes. However it is not implemented, and it is not a trivial 
> change to do so.
> 
If you do that (and implement a position dependent epsilon_r that is not 
1) your system will most likely explode. Using epsilon_r different from 
1 means that the weighting between Coulomb and Van der Waals forces will 
be different. For e.g. water e_r > 1 will make the system explode, e_r < 
1 will make it implode. Your choice.

-- 
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