Kinetic stability and energetics of simulated glasses created by constant pressure cooling

TL;DR

This study uses computer simulations to compare the stability and energetics of glasses formed under constant pressure versus constant volume cooling, revealing that constant pressure cooling yields more stable glasses with lower energies.

Contribution

It provides a systematic comparison of glass stability and energetics under constant pressure and volume cooling conditions using simulation data.

Findings

Constant pressure cooling produces glasses with higher stability ratios.

Glasses cooled at constant pressure have lower potential and inherent structure energies.

Stability improves with slower cooling rates under constant pressure.

Abstract

We use computer simulations to study the cooling rate dependence of the stability and energetics of model glasses created at constant pressure conditions and compare the results with glasses formed at constant volume conditions. To examine the stability, we determine the time it takes for a glass cooled and reheated at constant pressure to transform back into a liquid, $t_{\mathrm{trans}}$, and calculate the stability ratio $S = t_{\mathrm{trans}}/\tau_\alpha$, where $\tau_\alpha$ is the equilibrium relaxation time of the liquid. We find that, for slow enough cooling rates, cooling and reheating at constant pressure results in a larger stability ratio $S$ than for cooling and reheating at constant volume. We also compare the energetics of glasses obtained by cooling while maintaining constant pressure with those of glasses created by cooling from the same state point while maintaining constant volume. We find that cooling at constant pressure results in glasses with lower average potential energy and average inherent structure energy. We note that in model simulations of the vapor deposition process glasses are created under constant pressure conditions, and thus they should be compared to glasses obtained by constant pressure cooling.