A self-consistent density-functional approach for homogeneous and inhomogeneous classical fluids

A self-consistent density-functional theory (DFT) for homogeneous and inhomogeneous classical fluids is presented using the density-functional Taylor expansion of an effective density that is introduced to describe the intrinsic excess free-energy functional. The first-order density expansion of the effective density around the uniform bulk density provides the same intrinsic excess chemical potential as the weighted density-functional approach proposed by Patra and Ghosh [J. Chem. Phys. 116 (2002) 8509]. The density-expansion coefficient is determined in a self-consistent manner by using Percus' relation between the pair correlation function and the density distribution function. The pair correlation functions for hard-sphere (HS) and Lennard-Jones (LJ) fluids as well as one-component plasma obtained from the self-consistent DFT are compared with the simulation results. The DFT with the self-consistent expansion coefficient is applied to calculate density distribution functions for the inhomogeneous fluids, interacting via the HS and LJ potentials, under external fields such as confinement in several geometries.