Berlin 2012 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 10: Interfaces and Thin Films II

CPP 10.12: Talk

Tuesday, March 27, 2012, 12:45–13:00, C 130

The mesoscopic structure of liquid–vapour interfaces — •Felix Höfling and Siegfried Dietrich — Max-Planck-Institut für Intelligente Systeme, Heisenbergstraße 3, 70569 Stuttgart, and Institut für Theoretische und Angewandte Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart

The interfacial region between coexisting phases, e.g., between liquid and vapour, is broadened and roughened by thermal fluctuations. The spectrum of these fluctuations diverges for large wavelengths according to capillary wave theory; deviations have been predicted by density functional theory for inhomogeneous fluids [1]. In particular, an enhancement of fluctuations at mesoscopic wavenumbers is expected due to the long-ranged nature of the intermolecular dispersion forces. These predictions have been supported by scattering experiments, but previous computer simulations find a monotone spectrum.

We have performed extensive simulations for a simple liquid with Lennard–Jones interactions truncated at long distance. The investigation of large system sizes was considerably accelerated by a specifically developed simulation package employing high-end graphics processors [2]. Introducing an interfacial structure factor, the wavenumber-dependent surface tension is derived. It develops a maximum at mesoscopic scales as temperature is increased, indicating a relative suppression of fluctuations. We argue that the expected minimum may be masked by the emerging maximum.

[1] K. Mecke and S. Dietrich, Phys. Rev. E 59, 6766 (1999).

[2] P. Colberg and F. Höfling, Comp. Phys. Comm. 182, 1120 (2011).