Linking rigidity transitions with enthalpic changes at the glass transition and the fragility of glass-forming liquids

TL;DR

This study uses Monte Carlo simulations of a Keating-like model to explore how rigidity influences the glass transition and fragility, revealing that isostatic rigidity correlates with strong glass-forming behavior and minimal enthalpic changes.

Contribution

It establishes a link between rigidity, enthalpic changes, and fragility in glasses using a computational model, supported by experimental data on chalcogenide glasses.

Findings

Isostatic rigidity minimizes enthalpic changes during cooling.

Strong (Arrhenius-like) glass behavior occurs at optimal rigidity.

Experimental data on chalcogenide glasses support the theoretical predictions.

Abstract

A low temperature Monte Carlo dynamics of a Keating like oscillator model is used to study the relationship between the nature of glasses from the viewpoint of rigidity, and the strong-fragile behaviour of glass-forming liquids. The model shows that a Phillips optimal glass formation with minimal enthalpic changes is obtained under a cooling/annealing cycle when the system is optimally constrained by the harmonic interactions, i.e. when it is isostatically rigid. For these peculiar systems, the computed fragility shows also a minimum, which demonstrates that isostatically rigid glasses are strong (Arrhenius-like) glass-forming liquids. Experiments on chalcogenide and oxide glass-forming liquids are discussed under this new perspective and confirm the theoretical prediction for chalcogenide network glasses.