A simple model of wetting, prewetting, and layering transitions of structured liquids

A simple phenomenological model is proposed of wetting a substrate possessing a van der Waals long-range attraction by a liquid film which has the damped oscillatory surface density profile. At the liquid-vapor coexistence along the coexistence line, we predict successive transitions from incomplete wetting to no wetting, then to the complete wetting, as well as the usual wetting transition from incomplete wetting to complete wetting. However, at undersaturated pressures when the structure of the liquid becomes important, we predict not only the prewetting but also the layering transition. Simple criteria of those transitions using macroscopic and structural quantities are presented. The termination of the layering transition is explained by the capillary fluctuation. (C) 1998 Academic Press.