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Binding potentials for vapour nanobubbles on surfaces using density functional theory.

Research paper by Hanyu H Yin, David D Sibley, Andrew J AJ Archer

Indexed on: 16 Jul '19Published on: 13 Apr '19Published in: Journal of physics. Condensed matter : an Institute of Physics journal



Abstract

We calculate one-body density profiles of a simple model fluid in contact with a planar surface using density functional theory (DFT), in particular for the case where there is a vapour layer intruding between the wall and the bulk liquid. We apply the method of Hughes \emph{et al.}\ [J.\ Chem.\ Phys.\ {\bf 142}, 074702 (2015)] to calculate the density profiles for varying (specified) amounts of the vapour adsorbed at the wall. This is equivalent to varying the thickness $h$ of the vapour at the surface. From the resulting sequence of density profiles we calculate the thermodynamic grand potential as $h$ is varied and thereby determine the binding potential as a function of $h$. The binding potential obtained via this coarse-graining approach allows us to determine the disjoining pressure in the film and also to predict the shape of vapour nano-bubbles on the surface. Our microscopic DFT based approach captures information from length scales much smaller than some commonly used models in continuum mechanics. © 2019 IOP Publishing Ltd.