A molecular theory of liquid interfaces

We propose a site - site generalization of the Lovett - Mow - Buff-Wertheim integro-differential equation for the one-particle density distributions to polyatomic fluids. The method provides microscopic description of liquid interfaces of molecular fluids and solutions. It uses the inhomogeneous site - site direct correlation function of molecular fluid consistently constructed by nonlinear interpolation between the homogeneous ones. The site - site correlations of the coexisting bulk phases are obtained from the reference interaction site model (RISM) integral equation with our closure approximation. For illustration, we calculated the structure of the planar liquid - vapor as well as liquid - liquid interfaces of n-hexane and methanol at ambient conditions.