[gmx-users] Liquid-liquid interface and electric field

[David van der Spoel]

On 16/11/16 09:51, Gschwend Grégoire wrote:
> Hello everyone,
>
>
> I am trying to simulate an ion transfer at an interface between two immiscible electrolytes solutions. I have prepared a 5x5x5 nm box with the solvents and electrolytes. The system is stable and well equilibrated. The problem now is that when I apply an electric field in the z direction (normal to the interface)  it seems that nothing happens. By nothing I mean nothing different that with a simulation without electric field. I have tried many values for the magnitude of the field, even unrealistic values as high as 5 V/nm (while the ions should transfer around 0.5 V/nm max).
>
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> In the simulation I use periodic boudary conditions in all three directions. Thus, I was wondering if this was compatible with an electric field in the z direction. Indeed, the PBC implies that the potential is the same at z=0 and z=box_size, which implies that there is no field. Of couse the field could be periodic, but in the manual it is said that the frequency of the cosine is zero.
>
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> Should I use walls and PBC in x and y directions only?
No, that should not be necessary.
Please be more specific than "nothing happens". Does the ion not move at 
all? Then the temperature is zero. How long is the simulation?
>
>
> Thank you for your help and suggestions,
>
>
> Grégoire
>


-- 
David van der Spoel, Ph.D., Professor of Biology
Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone:	+46184714205.
spoel at xray.bmc.uu.se    http://folding.bmc.uu.se