The First-order mean-spherical approximation (FMSA) was combined with renormalization group (RG) transformation and applied to global phase behavior calculation. The analytical radial distribution function (RDF) and the direct correlation function (DCF), which were obtained from the FMSA, were applied to construct the density functional theory (DFT). In order to recover the bulk vapor and liquid densities of the Lennard-Jones fluid, the high-order terms of FMSA were included into the DFT to replace the ordinary second-order expansion. The method was extended to the associating fluid, and the calculated density profiles and interfacial tension are much better than those from ordinary DFT when compared with molecular simulation data.

Key words: interfacial tension, density functional theory, high-order FMSA expansion, DCF, RDF