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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 3: Colloids and Nanoparticles I: Structure

CPP 3.1: Vortrag

Montag, 26. März 2007, 10:00–10:15, H47

Structural crossover and connectivity in binary colloidal hard-sphere mixtures — Jörg Baumgartl¹, •Roel Dullens¹, Marjolein Dijkstra², Roland Roth³, and Clemens Bechinger¹ — ¹2. Physikalisches Institut, Universität Stuttgart, Germany — ²Soft Condensed Matter Group, Utrecht University, The Netherlands — ³Max-Planck-Institut für Metallforschung und Institut für Theoretische und Angewandte Physik, Stuttgart, Germany

Already the simplest conceivable multi-component system, i.e. a binary mixture of hard spheres, exhibits an exceedingly rich phenomenology in comparison to single-component systems. Recently, it has been predicted that the phase diagram is divided by a crossover line which distinguishes two regions where the oscillation wavelength of the pair correlation function in the asymptotic limit is either dominated by the diameter of the big spheres or that of the small spheres. Despite the generic character of this structural crossover, this effect has not been observed experimentally. This is the more surprising, because recent calculations demonstrate that the asymptotic regime starts already at intermediate ranges, implying that structural crossover should be visible at relatively small distances. In this work, we use confocal microscopy to investigate the structural crossover in a (high-packing fraction) binary colloidal model system. Furthermore, we address the question as to what the repercussions of the crossover on the structure of a binary fluid are. To this end, we analyze the fluid structure in terms of connectivity based on Delaunay triangulations. This analysis is extended to lower packing fractions using Monte-Carlo simulations.