Relaxation and physical aging in network glasses: a review

TL;DR

This review summarizes recent advances in understanding relaxation and aging in network glasses, highlighting experimental, theoretical, and simulation approaches, and emphasizing the role of network topology, rigidity, and heterogeneities in glass dynamics.

Contribution

It provides a comprehensive overview of the current state of research on relaxation and aging in network-forming glasses, integrating experimental, theoretical, and computational insights.

Findings

Network topology and rigidity critically influence glass relaxation.

Computer simulations reveal molecular-level dynamics and structure-related functions.

Spatial heterogeneities underpin dynamic heterogeneity in glasses.

Abstract

Recent progresses in the description of glassy relaxation and ageing are reviewed for the wide class of network-forming materials such as $GeO_2$, Ge$_x$Se$_{1-x}$, silicates (SiO$_2$-Na$_2$O) or borates (B$_2$O$_3$-Li$_2$O), all of them having an important usefulness in domestic, geological or optoelectronic applications. A brief introduction of the glass transition phenomenology is given, together with the salient features that are revealed both from theory and experiments. Standard experimental methods used for the characterization of the slowing down of the dynamics are reviewed. We then discuss the important role played by aspect of network topology and rigidity for the understanding of the relaxation of the glass transition, while also permitting analytical predictions of glass properties from simple and insightful models based on the network structure. We also emphasize the great utility of computer simulations which probe the dynamics at the molecular level, and permit to calculate various structure-related functions in connection with glassy relaxation and the physics of ageing which reveals the off-equilibrium nature of glasses. We discuss the notion of spatial variations of structure which leads to the picture of "{\em dynamic heterogeneities}", and recent results of this important topic for network glasses are also reviewed.