Hi, I am simulating a capacitor (in which the dielectric is liquid between the plates), with charged electrodes parallel to the xy plane. Because the system is effectively two-dimensional, I am using ewald_geometry = 3dc, which applies a force and potential correction in the z dimension, giving a pseudo 2-D Ewald summation.
However, I observe a drift in the electric potential between the plates. Specifically, I use g_potential to solve the Poisson equation and determine the electric potential as a function of the z coordinate. The liquid has a structure such that an electric double layer is formed, and this cancels off much of the electric field due to the charged electrodes. So, I would expect that the potential between the plates is constant (i.e., a plot of the electric potential Phi versus z is expected to be flat). This is in fact what I observe when I simulate the same system using another MD package, using exactly the same force field parameters and the analogous (same correction equations, just different code) force and potential correction in the z dimension to produce a pseudo 2-D Ewald summation: in that other MD package, the electric potential is constant (flat) between the capacitor plates. But in Gromacs (4.5.5), the potential is not constant (flat) between the plates; rather, it is linear with a non-zero slope. Has anyone else experienced such a "drift" in the electric potential when using a slab geometry and ewald_geometry = 3dc? Do you have any ideas of what might cause this and how I can fix this? Thank you very much. Andrew DeYoung Carnegie Mellon University -- gmx-users mailing list [email protected] http://lists.gromacs.org/mailman/listinfo/gmx-users Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/Search before posting! Please don't post (un)subscribe requests to the list. Use the www interface or send it to [email protected]. Can't post? Read http://www.gromacs.org/Support/Mailing_Lists
