Fragile Glasses Associated with a Dramatic Drop of Entropy under Supercooling

TL;DR

This study uses kinetic Monte Carlo simulations to explore how entropy drops in supercooled glasses relate to their kinetic fragility, revealing that more fragile glasses exhibit significant entropy reductions and slower dynamics.

Contribution

It demonstrates a correlation between thermodynamic entropy drops and kinetic fragility in structural glasses through simulation data.

Findings

Fragile glasses show dramatic entropy drops upon cooling.

Structural relaxation follows a decreasing trend in the stretching exponent with fragility.

Kinetic fragility correlates with thermodynamic fragility.

Abstract

We perform kinetic Monte Carlo simulations of a distinguishable-particle lattice model of structural glasses with random particle interactions. By varying the interaction distribution and the average particle hopping energy barrier, we obtain an extraordinarily wide range of kinetic fragility. A stretching exponent, characterizing structural relaxation, is found to decrease with the kinetic fragility in agreement with experiments. The most fragile glasses are those exhibiting low hopping barriers and, more importantly, dramatic drops of entropies upon cooling toward the glass transition temperatures. The entropy drops reduce possible kinetic pathways and lead to dramatic slowdowns in the dynamics. In addition, the kinetic fragility is shown to correlate with a thermodynamic fragility.