Density functional theory and the capillary evaporation of a liquid in a slit

Density functional theory is applied to a Lennard-Jones fluid near a single hard wall and in a slit formed by two walls. We use some simplified versio ns of the Wecks-Chandler-Andersen (WCA) and the Barker-Henderson (BH) theor ies. Only the most crude mean field version of the WCA theory, in which the hard-sphere correlation function is set equal to unity for all distances, seems useful. Use of the full WCA approximation is impractical because the effective hard-sphere diameter is density dependent. Generally, the best re sults are obtained using the BH macroscopic compressibility approximation. Our earlier study of "evaporation" of Lennard-Jones molecules in a slit is extended to other densities using the mean field theory. (C) 2000 Academic Press.