Dresden 2014 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 18: Wetting, Superamphiophobicity, Micro- and Nanofluidics I
CPP 18.3: Vortrag
Dienstag, 1. April 2014, 10:00–10:15, ZEU 222
Liquid drops on a surface: using density functional theory to calculate the binding potential and drop profiles and comparing with results from mesoscopic modelling — •Adam P. Hughes1, Uwe Thiele1,2, and Andrew J. Archer1 — 1Department of Mathematical Sciences, Loughborough University, UK — 2Institut für Theoretische Physik, Universität Münster, Germany
The contribution to the excess free energy for a film of liquid of thickness h on a solid surface, due to the interactions between the solid-liquid and liquid-gas interfaces is given by the binding potential, W(h). The precise form of W(h) determines whether or not the liquid wets the surface. Note that differentiating W(h) gives the Derjaguin or disjoining pressure. We develop a microscopic density functional theory (DFT) based method for calculating W(h), allowing us to relate the form of W(h) to the nature of the molecular interactions in the system. We present results using a simple lattice gas model to demonstrate the procedure. In order to describe non-uniform liquid films and drops, a mesoscopic free energy based on W(h) is often used. We calculate such film height profiles and also directly calculate using DFT the corresponding density profiles for liquid drops on surfaces. Comparing quantities such as the contact angle and also the shape of the drops, we find good agreement between the two methods. We also study in detail the effect on W(h) of truncating the range of the dispersion forces, both those between the fluid molecules and those between the fluid and wall. We find that truncating can have a significant effect on W(h) and the associated wetting behaviour of the fluid.