Phase Separation in Binary Fluid Mixture with Quenched Disorder

Quenched or frozen-in, structural disorder is ubiquitous in real experimental systems. Much of the progress is achieved in understanding the phase separation of such systems using diffusion-driven coarsening in Ising model with quenched disorder. But there is a paucity of research in the phase-separation kinetics in fluids with quenched disorder. In this letter, we present results from a detailed Molecular dynamics (MD) simulation the effects of randomly placed localized impurities on the phase separating kinetics of binary fluid mixture. Our system resembles the fluid imbibed into a porous medium. We observe a dramatic slowing down in the pattern formation with increasing pin particle concentration. The domain growth follows the power-law with a disorder-dependent exponent. Due to the energetically favorable positions, the domain boundary roughens which modifies the correlation function and structure factor to a non-Porod behavior. The correlation function and structure factor provide clear evidence that the superuniversality does not hold in our system

Phase separation and aging dynamics of binary liquids in porous media

We employ the state-of-the-art molecular dynamics simulations to study the kinetics of phase separation and aging phenomena of segregating binary fluid mixtures imbibed in porous materials. Different random porous structures are considered to understand the effect of pore morphology on coarsening dynamics. We find the effect of complex geometrical confinement resulting in the dramatic slowing down in the phase separation dynamics. The domain growth follows the power law with an exponent dependent on the porous host structure. After the transient period, a crossover to a slower domain growth is observed when the domain size becomes comparable to the pore size. Due to the geometric confinement, the correlation function and structure factor modify to a non-Porod behavior and violate the superuniversality hypothesis. The role of porous host structure on the nonequilibrium aging dynamics is studied qualitatively by computing the two-time order-parameter autocorrelation function. This quantity exhibits scaling laws with respect to the ratio of the domain length at the observation time and the age of the system. We find the scaling laws hold well for such confined segregating fluid mixtures