Simulation of surface-controlled phase separation in slit pores: diffusive Ginzburg-Landau kinetics versus Molecular Dynamics

Abstract

The phase separation kinetics of binary fluids in constrained geometry is a challenge for computer simulation, since nontrivial structure formation occurs extending from the atomic scale up to mesoscopic scales, and a very large range of time needs to be considered. One line of attack to this problem is to try nevertheless standard Molecular Dynamics (MD), another approach is to coarse-grain the model to apply a time-dependent nonlinear Ginzburg-Landau equation that is numerically integrated. For a symmetric binary mixture confined between two parallel walls that prefer one species, both approaches are applied and compared to each other. There occurs a nontrivial interplay between the formation of a stratified structure due to enrichment layers of the component preferred by the walls, and lateral phase separation. While the former process already occurs during the initial stages, the latter dominates during intermediate and late stages. The extent to which the two methods are equivalent when one suitably translates the time scales is critically discussed.