Berlin 2005 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 22: Colloids

CPP 22.4: Talk

Tuesday, March 8, 2005, 12:00–12:15, TU C243

Capillary waves in a model colloid-polymer mixture — •Richard Vink, Jürgen Horbach, and Kurt Binder — Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, D-55099 Mainz, Germany

It is well-known that colloid-polymer mixtures phase separate under certain conditions. This then leads to the formation of two phases, separated by an interface. Interesting physics occurs in the interface region. The interface is not flat, but displays wave-like fluctuations known as capillary waves. Recently, it became possible to directly observe these fluctuations in experiments.

In this talk, I will discuss how capillary waves can be studied in a computer simulation of a simple colloid-polymer mixture (the AO model).First, I will describe how the interface is extracted from the simulation data. Next, a Fourier analysis of the interface will be presented. For small wavevectors, the quadratic q-dependence of the capillary spectrum, as predicted by capillary wave theory, is confirmed. For higher wave-vectors, pronounced deviations appear, which seem to reflect the most dominant bulk fluctuations. More precisely, our simulations indicate that in the limit of large wave-vectors, the capillary spectrum and the bulk static structure factor are essentially the same.