Classical density functional theory (DFT) is a statistical mechanical theory for calculating the density profiles of the molecules in a liquid. It is widely used, for example, to study the density distribution of the molecules near a confining wall, the interfacial tension, wetting behavior, and many other properties of nonuniform liquids. DFT can, however, be somewhat daunting to students entering the field because of the many connections to other areas of liquid-state science that are required and used to develop the theories. Here, we give an introduction to some of the key ideas, based on a lattice-gas (Ising) model fluid. This approach builds on knowledge covered in most undergraduate statistical mechanics and thermodynamics courses, so students can quickly get to the stage of calculating density profiles, etc., for themselves. We derive a simple DFT for the lattice gas and present some typical results that can readily be calculated using the theory.
Funding
A.P.H. acknowledges support through a Loughborough
University Graduate School Studentship.
History
School
Science
Department
Mathematical Sciences
Published in
AMERICAN JOURNAL OF PHYSICS
Volume
82
Issue
12
Pages
1119 - 1129 (11)
Citation
HUGHES, A.P., ARCHER, A.J. and THIELE, U., 2014. An introduction to inhomogeneous liquids, density functional theory, and the wetting transition. American Journal of Physics, 82 (12), pp. 1119 - 1129.
Copyright 2014 American Institute of Physics/American Association of Physics Teachers. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in American Journal of Physics, 82 (12), pp. 1119 - 1129 and may be found at: http://dx.doi.org/10.1119/1.4890823