Simple model for liquid/liquid interfaces

The thermodynamics of a mixture of two types of dipolar spherical molecules with Yukawa interactions is investigated. When the cross-interaction of the two components is weaker than the self-interactions, the system tends to separate into two phases; each phase has a high concentration of one component and a smaller concentration of the other. The density profiles of the two components near the interface are calculated using the density functional formalism with the gradient approximation. The width of the interfacial region is of the order of a few molecular diameters, and is the greater the higher the concentration of the minority components in the two phases.