Spatiotemporal structures in aging and rejuvenating glasses

TL;DR

This paper models the development of complex spatiotemporal structures in aging and rejuvenating glasses by integrating theories of activated events and mobility transport, revealing distinct behaviors in aging versus rejuvenation processes.

Contribution

It introduces a combined theoretical framework to explain the formation of structures in glasses during aging and rejuvenation, highlighting the role of mobility fronts and transport mechanisms.

Findings

Rejuvenation involves propagating mobility fronts resembling flames.

Mobility transport modestly affects aging but significantly impacts rejuvenation.

The analogy with combustion theory estimates front propagation speeds.

Abstract

Complex spatiotemporal structures develop during the process of aging glasses after cooling and of rejuvenating glasses upon heating. The key to understanding these structures is the interplay between the activated reconfiguration events which generate mobility and the transport of mobility. These effects are both accounted for by combining the random first order transition theory of activated events with mode coupling theory in an inhomogeneous setting. The predicted modifications by mobility transport of the time course of the aging regime are modest. In contrast, the rejuvenation process is strongly affected through the propagation of fronts of enhanced mobility originating from the initial reconfiguration events. The structures in a rejuvenating glass resemble flames. An analysis along the lines of combustion theory provides an estimate of the front propagation speed. Heterogeneous rejuvenation naturally should occur for glasses with free surfaces. The analogy with combustion also provides a new way of looking at the uptake of diluents by glasses described by case II and super case II diffusion.