8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P5.100Wed 711:10-14:00Effective pair potentials for super-paramagnetic colloidsin rotating magnetic fieldsKathrin Müller, 1 Arash Nikoubashman, 2 Natan Osterman, 3 Dušan Babič, 4 JureDobnikar, 5 and Christos Likos 61 Theoretische Physik, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225,Düsseldorf, Germany2 Soft matter theory, TU Vienna, Wien, Austria3 Systems Biophysics, Ludwig-Maximilians-Universität München, München, Germany4 Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia5 Department of Chemistry, University of Cambridge, Cambridge, United Kingdom6 Computational Physics, University of Vienna, Wien, AustriaWe present the successful projection of the structure of classical fluids to effective pair potentialsfor a 2D system of super-paramagnetic colloids under a rotating external magnetic field. Knowingthe structure of a system in form of the radial distribution function from the experiments, weaim at finding a simple pair potential that reproduces the pair structure. To this end, we designand implement a search algorithm, which can seek for the right parameters of a given potential,resulting in the best fitting radial distribution function. The algorithm consists of a combinationof a numerically calculated 2D Fourier transform, different closure relations to solve the Ornstein-Zernike equation and a Genetic Algorithm to optimize the radial distribution function. We showthat this combination works well for finding the right parameters of typical used potentials, like theLennard-Jones Potential and the Yukawa Potential and of a combination of both. We extend theapproach to anisotropic (patchy) potentials in an effort to reproduce very unusual structures foundin experiments, such as network chains including a number of Y-junctions.100