Phase separation in a binary mixture confined between symmetric parallel plates: Capillary condensation transition near the bulk critical point

摘要

We investigate phase separation of near-critical binary mixtures between parallel symmetric walls in the strongnadsorption regime.We take into account the renormalization effect due to the critical fluctuations using the recentnlocal functional theory [Okamoto and Onuki, J. Chem. Phys. 136, 114704 (2012)]. In statics, a van der Waalsnloop is obtained in the relation between the average order parameter u0002ψu0003 in the film and the chemical potentialnwhen the temperature T is lower than the film critical temperature T canc (in the case of an upper critical solutionntemperature). In dynamics, we lower T below the capillary condensation line from above T canc . We calculate thensubsequent time development assuming no mass exchange between the film and the reservoir. In the early stage,nthe order parameter ψ changes only in the direction perpendicular to the walls. For sufficiently deep quenching,nsuch one-dimensional profiles become unstable with respect to the fluctuations varying in the lateral directions.nThe late-stage coarsening is then accelerated by the hydrodynamic interaction. A pancake domain of the phasendisfavored by the walls finally appears in the middle of the film.