6533b831fe1ef96bd1298348

RESEARCH PRODUCT

Wetting in fluid systems. Wetting and capillary condensation of lattice gases in thin film geometry

subject

description

Monte Carlo studies of lattice gas models with attractive interactions between nearest neighbors on a simple cubic lattice are carried out for a L×L×D geometry with two hard walls of size L×L and periodic boundary conditions parallel to the wall. Two types of short-range forces at the walls are considered: (i) Both walls are of the same type and exert an attractive force of the same strength (in Ising model terminology, surface fields HD = H1 occur). (ii) The walls differ, one attracts and the other repels particles, again with the same strength (HD = −H1). In the first case, capillary condensation occurs at a chemical potential differing from its value for phase coexistence in the bulk, and the (second-order) wetting transition that occurs for D∞ is rounded off. In the second case, an interface parallel to the walls is stabilized and we observe the interface delocalization transition predicted by Parry and Evans. A first attempt to study the nature of this “quasi wetting transition” by finite size scaling methods is reported, and discussed in the context of recent theories.