The instantaneous shear modulus in the shoving model

TL;DR

This paper clarifies that the relevant shear modulus in the shoving model is the experimentally measurable high-frequency plateau modulus, not the idealized instantaneous shear modulus, and compares different model versions using metallic glass data.

Contribution

It identifies the correct experimentally accessible shear modulus for the shoving model and compares multiple model formulations with experimental data.

Findings

The high-frequency plateau shear modulus correlates with relaxation times.

The original model shows a correlation with Poisson ratio.

The energy-landscape formulation minimizes the role of bulk modulus.

Abstract

We point out that the instantaneous shear modulus of the shoving model for the non-Arrhenius temperature dependence of viscous liquids' relaxation time is the experimentally accessible high-frequency plateau modulus, not the idealized instantaneous affine shear modulus that cannot be measured. Data for a large selection of metallic glasses are compared to three different versions of the shoving model. The original shear-modulus based version shows a slight correlation to the Poisson ratio, which is eliminated by the energy-landscape formulation of the model in which the bulk modulus plays a minor role.