Berlin 2012 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 28: Colloids and Complex Liquids I

CPP 28.11: Talk

Wednesday, March 28, 2012, 18:00–18:15, C 130

A Poisson-Boltzmann solution of the two-colloid problem — •Alexander Schlaich, Stefan Kesselheim, Marcello Sega, and Christian Holm — Institut für Computerphysik, Universität Stuttgart, Pfaffenwaldring 27, 70569, Stuttgart, Deutschland

The force acting between colloidal particles in ionic solutions is often modeled in terms of the nonlinear Poisson-Boltzmann equation. A solution can be obtained using standard finite element methods, however usual assumptions, like a constant surface charge density at the particle’s surface or a constant surface potential, are not able to reproduce the correct potential if the typical distance becomes small such that the Debye layers overlap.

To determine these boundary conditions, we use an iterative procedure which also accounts for a jump of the dielectric constant at the particles surface. We compare our results to theoretical predictions and the results of coarse-grained molecular dynamics simulations using explicit ions. The efficient parallel implementation, using the Distributed and Unified Numerics Environment DUNE, also allows us to consider the question of pairwise additivity in the Poisson-Boltzmann description.