Berlin 2008 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 26: Micro and Nano Fluidics I: Liquids at structured materials
CPP 26.7: Vortrag
Mittwoch, 27. Februar 2008, 15:45–16:00, C 264
Intrusion of fluids into nanogrooves — Holger Bohlen1, Andrew O. Parry2, Enrique Diaz-Herrera3, and •Martin Schoen1 — 1Stranski-Lab. f. Physikal. und Theor. Chemie, Technische Universität Berlin, GERMANY — 2Dept. of Mathematics, Imperial College, London, UK — 3Dept. de Fisica, UNAM, Mexico City, Mexico
We study the shape of gas-liquid interfaces forming inside rectangular nanogrooves. On account of purely repulsive fluid-substrate interactions the confining walls are dry (i.e., wet by vapor) and a liquid-vapor interface intrudes into the nanogrooves to a distance determined by the pressure. By means of Monte Carlo simulations in the grand canonical ensemble (GCEMC) we obtain the density ρ(z) along the midline (x=0) of the nanogroove for various geometries (i.e., depths D and widths L) of the nanogroove. We analyze the density profiles with the aid of an analytic expression which we obtain through a transfer-matrix treatment of an one-dimensional effective interface Hamiltonian. Besides geometrical parameters such as D and L the resulting analytic expression depends on temperature T, densities of coexisting gas and liquid phases in the bulk ρxg,l and the interfacial tension γ. The latter three quantities are determined in independent molecular dynamics simulations of planar gas-liquid interfaces. Our results indicate that the analytic formula provides an excellent representation of ρ(z) as long as L is sufficiently small. At larger L the meniscus of the intruding liquid flattens. Under these conditions the transfer-matrix analysis is no longer adequate and the agreement between GCEMC data and the analytic treatment is less satisfactory.