Phase separation in confined systems

We review the current state of knowledge of phase separation and phase Aequilibria in porous materials. Our emphasis is on fundamental studies of simple fluids A(composed of small, neutral molecules) and well-characterized materials. While theoretical and molecular simulation studies are stressed, we also survey experimental investigations that Aare fundamental in nature. Following a brief survey of the most useful theoretical and simulation Amethods, we describe the nature of gas-liquid (capillary condensation), layering, Aliquid-liquid and freezing/melting transitions. In each case studies for simple pore geometries, and also Amore complex ones where available, are discussed. While a reasonably good understanding Ais available for phase equilibria of pure adsorbates in simple pore geometries, there is a Aneed to extend the models to more complex pore geometries that include effects of chemical and Ageometrical heterogeneity and connectivity. In addition, with the exception of liquid-liquid Aequilibria, little work has been done so far on phase separation for mixtures in porous media.