Liquid-liquid phase separation in cylindrical pores: Quench molecular dynamics and Monte Carlo simulations

We have studied the liquid-liquid phase separation of a binary mixture confined in three different cylindrical pores by several simulation methods. The phase diagrams of the fluid mixture in the three pores were determined using histogram-biased semigrand Monte Carlo simulations, and the kinetics of phase separation of the confined liquid mixture were studied using quench molecular dynamics. In these systems, the interactions between the two fluids and the pore wall are identical so that no wetting occurs and the fluid separates into a series of pluglike domains after a temperature quench. We have determined that the growth of these domains is given by a power law for systems near to their critical temperature, while for deeper quenches it proceeds by a power law at short times which crosses over to a slower growth when the plug-shaped domains are large enough to completely block the pore. Domains in these systems are shown to grow by a condensation mechanism. Using a simple thermodynamic model we analyze the P(X) probability distributions from our Monte Carlo simulations, and estimate the equilibrium domain lengths in two pores over a range of temperature. These lengths are larger than those reached in our molecular dynamics simulations. In order to assess these estimations, we have performed very long canonical Monte Carlo simulations to directly determine the equilibrium domain lengths in a few of these pores.