Slow stretched-exponential and fast compressed-exponential relaxation from local event dynamics

TL;DR

This paper introduces an atomistic model explaining both slow stretched-exponential and fast compressed-exponential relaxation in liquids and glasses, capturing temperature dependence and the crossover observed experimentally.

Contribution

The model uniquely links local relaxation events with elastic interactions to explain different relaxation regimes and their temperature-dependent behaviors.

Findings

Predicts temperature-dependent SER and CER behaviors.

Recovers simple exponential decay at high temperatures.

Reproduces observed SER to CER crossover in metallic glasses.

Abstract

We propose an atomistic model for correlated particle dynamics in liquids and glasses predicting both slow stretched-exponential relaxation (SER) and fast compressed-exponential relaxation (CER). The model is based on the key concept of elastically interacting local relaxation events. SER is related to slowing down of dynamics of local relaxation events as a result of this interaction, whereas CER is related to the avalanche-like dynamics in the low-temperature glass state. The model predicts temperature dependence of SER and CER seen experimentally and recovers the simple, Debye, exponential decay at high temperature. Finally, we reproduce SER to CER crossover across the glass transition recently observed in metallic glasses.