Visualizing the collective motions responsible for the α and β relaxations in a model glass

Maps of the spatial distributions of the relaxation times are obtained from Monte Carlo simulations of the facilitated kinetic Ising model. The {β} relaxation, acting over short and intermediate time scales, is observed to occur in localized pockets. The slow {α} relaxation is governed by the fraction of these pockets which are free to move. This physical picture is able to account for the non-Arrhenius temperature dependence of the time scales of the {α} process, the scaling of the relaxation function in the {β} region, and the value of the relaxation function at the crossover time.