Dresden 2009 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 28: POSTERS Interfaces and Thin Films

CPP 28.19: Poster

Mittwoch, 25. März 2009, 17:00–19:00, P3

The bending rigidity of the liquid/vapour interface of water — •Felix Sedlmeier, Dominik Horinek, and Roland R. Netz — Physik Department, Technische Universität München, 85748 Garching, Deutschland

Whenever two liquid phases are in contact, thermally excited fluctuations of the interface position, i.e. capillary waves, occur. At large length scales, they are well described by a constant interfacial tension in the framework of capillary wave theory. On smaller scales, however, deviations from capillary wave theory arise, which lead to an effective surface tension that is a function of the wave vector of the excitation modes. The coefficient of the quadratic order term of the effective surface tension can be identified with Helfrich's bending rigidity, the sign and magnitude of which has been a long standing issue in theoretical as well as experimental research. Also, simulation studies of simple liquids have not given a conclusive answer yet. One of the main problems in the analysis of capillary waves at liquid interfaces is that at small scales interfacial fluctuations are entangled with bulk-like density fluctuations. For an unambiguous determination of the bending rigidity, these contributions have to be separated. We present results from large scale molecular dynamics simulations that elucidate the effect of this entanglement and give quantitative results for the bending rigidity of the liquid/vapour interface of water.