Fluid Mixtures In Narrow Cylindrical Pores - Computer-simulation and Theory

We discuss the simulation results of phase separation of a binary Lennard- Jones mixture in a cylindrical pore induced by a temperature quench. The liquid-vapor phase separation proceeds in two stages involving different time scales. First, following the growth of density fluctuations, mechanical equilibrium is rapidly established when the system splits into a dense and a dilute phase. Material equilibrium, however, is reached via the mutual diffusion of the two components and this proceeds on an appreciably longer time scale. We briefly address the rounding of a first-order phase transition in a cylinder. In particular, we explore the possibility of multiple domains of gas and liquid when the aspect ratio is very large. Finally, we introduce an extension of Tarazona's nonlocal density function to binary mixtures of arbitrary size. The new theory is successfully tested against simulations of an additive hard-sphere mixture against a hard wall.