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

Gschwend Grégoire gregoire.gschwend at epfl.ch
Wed Nov 16 09:51:23 CET 2016

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).

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.

Should I use walls and PBC in x and y directions only?

Thank you for your help and suggestions,


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