Density functional theory of inhomogeneous liquids. II. A fundamental measure approach.
Previously, it has been shown that the direct correlation function for a Lennard-Jones fluid could be modeled by a sum of that for hard-spheres, a mean-field tail, and a simple linear correction in the core region constructed so as to reproduce the (known) bulk equation of state of the fluid [Lutsko, J. Chem. Phys. 127, 054701 (2007)]. Here, this model is combined with ideas from the fundamental measure theory to construct a density functional theory for the free energy. The theory is shown to accurately describe a range of inhomogeneous conditions including the liquid vapor interface, the fluid in contact with a hard wall, and a fluid confined in a slit pore. The theory gives quantitatively accurate predictions for the surface tension, including its dependence on the potential cutoff. It also obeys two important exact conditions: That relating the direct correlation function to the functional derivative of the free energy with respect to density and the wall theorem.
Physics Department CP 231, Université Libre de Bruxelles, Blvd. du Triomphe, Brussels, Belgium. jlutsko@ulb.ac.be
James F
JF
Lutsko