A perturbative density functional theory of inhomogeneous fluid mixture

A simple perturbative density functional approach has been developed for an inhomogeneous fluid mixture based on a functional Taylor expansion of the free energy in terms of the density inhomogeneity up to third order. A new approximation for the three-body correlation function for the mixture is pr oposed and the theory is applied to predict the structure of hard-sphere mi xture near a hard wall. The calculated density profiles for both the compon ents are found to agree quite well with the corresponding computer simulati on results. This theory for an inhomogeneous fluid is also applied to study the structure of a homogeneous hard-sphere mixture, for which the calculat ed radial distribution functions are found to compare well with the corresp onding results obtained from the Fourier transform of the structure factors from the Percus-Yevick theory of liquid mixtures. (C) 1999 American Instit ute of Physics. [S0021-9606(99)50614-4].