Microscopic Picture of Aging in SiO2

We investigate the aging dynamics of amorphous SiO2 via molecular dynamics simulations of a quench from a high temperature T-i to a lower temperature T-f. We obtain a microscopic picture of aging dynamics by analyzing single particle trajectories, identifying jump events when a particle escapes the cage formed by its neighbors, and determining how these jumps depend on the waiting time t(w), the time elapsed since the temperature quench to T-f. We find that the only t(w)-dependent microscopic quantity is the number of jumping particles per unit time, which decreases with age. Similar to previous studies for fragile glass formers, we show here for the strong glass former SiO2 that neither the distribution of jump lengths nor the distribution of times spent in the cage are t(w) dependent. We conclude that the microscopic aging dynamics is surprisingly similar for fragile and strong glass formers. DOI: 10.1103/PhysRevLett.110.017801