Temperature-Dependent Defect Dynamics in the Network Glass SiO2

TL;DR

This study examines how defect dynamics in SiO2 glass vary with temperature, revealing that defect lifetimes and structural rearrangements are strongly temperature-dependent and coupled, providing insights into the microscopic behavior of glassy materials.

Contribution

It introduces a detailed analysis of defect lifetimes and their temperature dependence in SiO2, highlighting the coupling between atomic jumps and defect creation or annihilation.

Findings

Defect lifetimes are temperature dependent and consistent with activated processes.

Most common defects are OO neighbors with long lifetimes.

Structural rearrangements are strongly correlated with defect dynamics.

Abstract

We investigate the long time dynamics of a strong glass former, SiO2, below the glass transition temperature by averaging single particle trajectories over time windows which comprise roughly 100 particle oscillations. The structure on this coarse-grained time scale is very well defined in terms of coordination numbers, allowing us to identify ill-coordinated atoms, called defects in the following. The most numerous defects are OO neighbors, whose lifetimes are comparable to the equilibration time at low temperature. On the other hand SiO and OSi defects are very rare and short lived. The lifetime of defects is found to be strongly temperature dependent, consistent with activated processes. Single-particle jumps give rise to local structural rearrangements. We show that in SiO2 these structural rearrangements are coupled to the creation or annihilation of defects, giving rise to very strong correlations of jumping atoms and defects.