Inverse Systems - Confined Fluids: Phase Diagram and Metastability.

When a fluid is confined by solid surfaces, its equilibrium properties are modified by several mechanisms. One point is that surface effects become quantitatively significant compared with bulk effects, and for this reason, solid-fluid interactions begin to compete with fluid-fluid interactions in the determination of the phase diagram of the fluid. If the fluid-solid attraction is sufficient, confinement can stabilise a liquid phase that would have evaporated in the absence of the solid. The liquid-vapour transition is modified by confinement. The same goes for the melting-solidification transition. For high levels of confinement, such that the mean size of pores becomes of the same order of magnitude as density inhomogeneities in the fluid, the liquid can no longer be distinguished from its vapour: the critical point is modified by confinement, the critical temperature decreasing with pore size. Finally, for the ultimate confinement, in which pore sizes are comparable with the size of molecules in the fluid, the very notion of fluid is no longer applicable. In the following, we shall review these various degrees of confinement and the resulting modifications of physical properties. [ABSTRACT FROM AUTHOR]