Effect of long-range forces on wetting near bulk critical temperatures: An Ising-model study

Numerical and analytic studies of the effect of long-range (i.e., algebraic) potentials on wetting transitions near bulk critical temperatures are presented within mean-field theory on an Ising lattice gas. The ordinary, special, and extraordinary points of the short-ranged-potential theory of Nakanishi and Fisher remain. However, for a long-ranged potential favoring wetting, certain transitions at coexistence are considerably altered: Critical wetting transitions become first order, critical drying transitions vanish, first-order drying transitions become partial drying transitions, and drying occurs only at the bulk critical temperature, in contradiction to the Cahn theory. Exponents, for the most part, remain the same as for the short-ranged case. Phase diagrams and density profiles are given, and a relevant experiment is discussed.