Kinetics of Order-Disorder Transitions in Binary Mixtures: A Monte Carlo Study

We study ordering kinetics in symmetric and asymmetric binary mixtures, undergoing an order-disorder transition below the critical temperature. We model the microscopic dynamics via an anti-ferromagnetic Ising model with Kawasaki spin-exchange kinetics. This conserves the composition but the order parameter, (staggered magnetization) is not a conserved quantity. The order-parameter correlation function shows dynamical scaling, and the scaling function is independent of mixture composition. The average domain size exhibits power law growth: L(t) ∼ t^α. The asymptotic growth regime has α = ½, though there can be prolonged transients with α < ½ for asymmetric mixtures. Our unambiguous observation of the asymptotic universal regime is facilitated by use of an accelerated Monte Carlo technique. (paper)