Estimation of the equilibrium free energy for glasses using the Jarzynski equality

TL;DR

This paper demonstrates that the Jarzynski equality can be used to estimate the free energy of glasses from nonequilibrium simulations, providing a viable alternative to thermodynamic integration which fails in such systems.

Contribution

The study shows that the Jarzynski relation can accurately estimate free energy in glasses, where traditional methods are ineffective, expanding its applicability to nonequilibrium systems.

Findings

Jarzynski estimates match extrapolated supercooled liquid values in glasses.

The method provides plausible free-energy estimates for glasses from nonequilibrium data.

The approach is potentially useful for gels and jammed structures.

Abstract

The free energy of glasses cannot be estimated using thermodynamic integration, as glasses are intrinsically not in equilibrium. We present numerical simulations showing that, in contrast, plausible free-energy estimates of a Kob-Andersen glass can be obtained using the Jarzynski relation. Using the Jarzynski relation, we also compute the chemical potential difference of the two components of this system, and find that, in the glassy regime, the Jarzynski estimate matches well with the extrapolated value of the supercooled liquid. Our findings are of broader interest as they show that the Jarzynski method can be used under conditions where the thermodynamic integration approach, which is normally more accurate, breaks down completely. Systems where such an approach might be useful are gels and jammed, glassy structures formed by compression.