Global Phase Diagram for the Wetting Transition at Interfaces in Fluid Mixtures

The authors analyze the wetting behavior at interfaces of three-phase equilibria exhibited by a fluid with two independent densities when described in mean field. The calculation treats nonuniformities exactly and regions are identified in interaction space where first- or second-order transitions or no transitions occur. Sullivan's model of the fluid-solid interface is obtained as a limiting case, but the global phase diagram is qualitatively different from that pertaining to a system described by one bulk order parameter plus two surface fields.