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From: | Axel Arnold |
Subject: | Re: [ESPResSo-users] Few quick questions. Electrostatics, LB. |
Date: | Tue, 3 Feb 2015 15:15:01 +0100 |
Hi!
The algorithm you need depends on the boundary conditions that apply to your system. 3d periodic boundary conditions require P3M, 2d+h-periodic bc require MMM2D or ELC + P3M. Nonperiodic bc require to use the Debye-Huckel potential as bare Coulomb interaction.
That is correct, if periodic boundary conditions apply perpendicular to your charge array. As a charge array exerts a constant force up to sign, you don’t get any force with two like-charged parallel plates, which is what periodic boundaries make out of your setup. You might first want to rethink the physics of your system... Btw, that is also the reason why the plate constraint only supports being perpendicular to the z-axis. If you use the plate, you necessarily need periodic boundary conditions parallel to the plate (otherwise the used formula is wrong), but you cannot have periodic boundary conditions in perpendicular direction. That leaves only MMM2D and ELC as algorithms, which both use the z-coordinate as the nonperiodic coordinate. Best, Axel
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JP Dr. Axel Arnold ICP, Universität Stuttgart Allmandring 3 70569 Stuttgart, Germany Email: address@hidden Phone: +49 711 685 67609 |
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