(178s) Using Molecular Simulations to Understand Wetting of Fluid Mixtures

Fluid mixtures can exhibit a rich variety of wetting behavior in the vicinity of a solid surface. This diversity is due, in part, to the presence of multiple species, which allow for the possibility of liquid-vapor as well as liquid-liquid phase equilibrium. In this presentation we describe our recent efforts to study the wetting behavior of mixtures via molecular simulation. We focus on methodological developments that enable one to compute interfacial properties of fluid mixtures in an efficient manner. Our basic approach involves calculating the surface excess free energy (also known as the interface potential) as a function of the surface density of the fluid. The interface potential provides information regarding qualitative wetting features (such as wetting regime and the order of wetting transition) as well as access to quantitative information, such as the contact angle and interfacial tensions. We outline several strategies for acquiring the components of the interface potential that are necessary to evaluate interfacial properties of interest. We demonstrate the utility of these methods by computing interfacial properties of different Lennard-Jones mixtures which display i) simple, ii) azeotropy, iii) and liquid-liquid phase separation in the bulk phase. We also discuss how these techniques can be used to understand the wetting behavior of model oil-water systems.