The Angell Plot from the Potential Energy Landscape Perspective

TL;DR

This paper introduces a thermodynamic model based on the potential energy landscape to explain the Angell plot, revealing a linear relationship between key parameters and distinguishing fragile and strong glasses.

Contribution

It develops a novel PEL-based model that fits experimental and molecular-dynamics data, linking relaxation times to barrier distributions and differentiating glass types.

Findings

Effective barrier and width parameters are linearly related across glasses.

Fragile and strong glasses occupy distinct regions in the parameter space.

The model accurately fits a wide range of experimental data.

Abstract

Within the scenario of the potential energy landscape (PEL), a thermodynamic model has been developed to uncover the physics behind the Angell plot. In our model, by separating the barrier distribution in PELs into a Gaussian-like and a power-law form, we obtain a general relationship between the relaxation time and the temperature. The wide range of the experimental data in the Angell plot, as well as the molecular-dynamics data, can be excellently fitted by two characteristic parameters, the effective barrier ({\omega}) and the effective width ({\sigma}) of a Gaussian-like distribution. More importantly, the fitted {\omega} and {\sigma}^2 for all glasses are found to have a simple linear relationship within a very narrow band, and fragile and strong glasses are well separated in the {\omega}-{\sigma}^2 plot, which indicates that glassy states only appear in a specific region of the PEL.