The Role of Local Structure in the Enhanced Dynamics of Deformed Glasses

TL;DR

This paper extends the Eyring model for amorphous solids by linking activation volume to local structural softness, revealing stress effects depend on local structure and influence molecular mobility.

Contribution

It introduces a machine-learned softness field to connect activation volume with local structure, enhancing understanding of stress-induced mobility changes in glasses.

Findings

Stress effects on mobility are inhomogeneous and structure-dependent.

Softness correlates with activation volume and relaxation dynamics.

Narrower relaxation time distribution under stress observed.

Abstract

External stress can accelerate molecular mobility of amorphous solids by several orders of magnitude. The changes in mobility are commonly interpreted through the Eyring model, which invokes an empirical activation volume whose origin remains poorly understood. Here, we analyze constant-stress molecular dynamics simulations and propose an extension of the Eyring model with a machine-learned field, softness. Our model connects the activation volume, an empirical parameter, to a structural property (softness). We show that stress has an inhomogeneous effect on the mobility that depends on local structure, which explains the narrower distribution of relaxation time observed under stress.