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

P7.42Thu 811:10-14:00The mesoscopic structure of liquid-vapour interfacesFelix Höfling 1 and Siegfried Dietrich 11 Max-Planck-Institut Stuttgart, Heisenbergstr. 3, 71229, Stuttgart, GermanyThe interfacial region between coexisting phases, e.g. , between liquid and vapour, is broadenedand roughened by thermal fluctuations. The spectrum of these fluctuations diverges for largewavelengths according to the phenomenological capillary wave theory (CWT). Deviations fromCWT 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-rangednature of the intermolecular dispersion forces. These predictions have been supported by scatteringexperiments in terms of a wavenumber-dependent surface tension. Previous computer simulations,however, disagree with these findings. We have performed molecular dynamics simulations fora simple liquid of up to one million particles interacting via a truncated Lennard-Jones potential.The investigation of such big systems was considerably accelerated by a specifically developedsimulation package employing high-end graphics processors [2]. An interfacial structure factoris introduced, the small-wavenumber behaviour of which encodes the capillary wave spectrum.This leads to an alternative definition of the wavenumber-dependent surface tension. The obtaineddata are compared to results from the usual definition based on height-height correlations of theintrinsic density profile. Finally, we discuss the position-dependent density-density correlationfunction H q (z 1 , z 2 ) and test a factorisation property which was proposed for small wavenumbers.[1] K. Mecke and S. Dietrich, Phys. Rev. E 59, 6766 (1999).[2] P. Colberg and F. Höfling, Comp. Phys. Comm. 182, 1120 (2011).42