Microscopic picture of aging in SiO2

TL;DR

This study uses molecular dynamics simulations to analyze the microscopic aging process in amorphous SiO2, revealing that the number of particle jumps decreases with age while jump characteristics remain unchanged, similar to fragile glass formers.

Contribution

It provides a detailed microscopic picture of aging in a strong glass former, showing that jump distributions are independent of age, which was previously observed mainly in fragile glasses.

Findings

Number of jumping particles decreases with age

Jump length and cage time distributions are age-independent

Microscopic aging behavior is similar in strong and fragile glasses

Abstract

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 by 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.