Long ranged correlations at a solid-fluid interface A signature of the approach to complete wetting

Abstract

We have investigated the behaviour of the pairwise distribution function for Sullivan's model of a gas adsorbed on a solid substrate. We show that in the approach to complete wetting, when a thick film of liquid density is adsorbed on the substrate, long ranged transverse correlations (parallel to the surface) develop at the edge of the film where the density profile of the fluid resembles that of a liquid-gas interface. The long ranged correlations can be attributed to damped capillary-wave-like fluctuations; for a class I wetting situation the damping decreases and the range of the correlations increases and ultimately diverges as the bulk gas pressure approaches the saturated vapour pressure.

Our analysis provides a physical explanation of the long ranged transverse correlations calculated by Foiles and Ashcroft in their recent study of a model of argon at a carbon dioxide substrate. We also predict that long range transverse correlations will occur for the case of adsorption from a dense liquid provided the solid-fluid potential is such that a thick film of gas forms between the substrate and the bulk liquid.