Bulk and shear relaxation in glasses and highly viscous liquids

TL;DR

This paper presents a theoretical calculation of the ratio of coupling strengths of relaxational processes to compression and shear in glasses, comparing results with experimental data on low-temperature tunneling states and the glass transition.

Contribution

It introduces a new theoretical approach based on the Eshelby model to quantify relaxational couplings in glasses and viscous liquids, linking microscopic rearrangements to macroscopic responses.

Findings

Calculated coupling ratio matches experimental data for tunneling states.

The model explains the Prigogine-Defay ratio at the glass transition.

Provides insight into the microscopic origins of relaxation in glasses.

Abstract

The ratio between the couplings of a relaxational process to compression and shear, respectively, is calculated in the Eshelby picture of structural rearrangements within a surrounding elastic matrix, assuming a constant density of stable structures in distortion space. The result is compared to experimental data for the low-temperature tunneling states in glasses and to Prigogine-Defay data at the glass transition from the literature.