The wetting transition associated with the adsorption of a gas on a rough surface

The effect of surface roughness on the wetting transition of a Lennard-Jone s 12-6 gas adsorbed on a rough surface that consists of a rough layer on a smooth substrate is studied. The gas molecules interact with the substrate by a 9-3 potential. The rough layer has a variable thickness and consists o f a disordered quenched matrix of hard spheres. Two repulsive interactions between the gas molecules and the matrix molecules are considered. Even at low matrix densities, the density thickness and the nature of the gas-matri x interaction have a significant effect on the adsorption isotherms and wet ting transition. As the density or thickness of the matrix layer increases, the adsorption isotherms pass from wetting to a prewetting transition and, if the layer is dense or thick enough, to partial wetting. However, the pr ewetting transition remains first-order.