Stretched Exponential Relaxation of Glasses at Low Temperature

TL;DR

This paper introduces a new simulation method to study long-term glass relaxation at room temperature, revealing stretched exponential energy relaxation consistent with theoretical models and observing volume relaxation linked to the mixed alkali effect.

Contribution

A novel atomistic simulation approach enabling direct observation of long-term glass relaxation dynamics at room temperature.

Findings

Energy relaxation follows a stretched exponential decay with β=3/5.

Volume relaxation occurs independently of energy relaxation.

Volume relaxation is associated with the mixed alkali effect.

Abstract

The question of whether glass continues to relax at low temperature is of fundamental and practical interest. Here, we report a novel atomistic simulation method allowing us to directly access the long-term dynamics of glass relaxation at room temperature. We find that the potential energy relaxation follows a stretched exponential decay, with a stretching exponent $\beta = 3/5$, as predicted by Phillips' diffusion-trap model. Interestingly, volume relaxation is also found. However, it is not correlated to the energy relaxation, but is rather a manifestation of the mixed alkali effect.