Absence of Thermodynamic Phase Transition in a Model Glass Former

TL;DR

This study uses advanced Monte Carlo simulations to investigate whether a thermodynamic phase transition underlies the glass transition in a 2D hard disc system, finding no evidence of such a transition and suggesting the glass is thermodynamically similar to the liquid.

Contribution

It demonstrates that there is no thermodynamic phase transition in a model glass former, challenging theories that link the glass transition to an underlying thermodynamic change.

Findings

No thermodynamic transition detected up to high densities

Glass and liquid are thermodynamically indistinguishable

Advanced Monte Carlo method enables equilibrium in glassy phase

Abstract

The glass transition can simply be viewed as the point at which the viscosity of a structurally disordered liquid reaches 10^{13} Poise [1]. This definition is operational but it sidesteps fundamental controversies about the glass: Is the transition a purely dynamical phenomenon [2]? This would mean that ergodicity gets broken, but that thermodynamic properties of the liquid remain unchanged across the transition if determined as thermodynamic equilibrium averages over the whole phase space. The opposite view [3-6] claims that an underlying thermodynamic phase transition is responsible for the dramatic slowdown at the liquid-glass boundary. Such a phase transition (which shows up in proper equilibrium phase space averages) would trigger the dynamic standstill, and then get masked by it. A recent Monte Carlo algorithm [7] introduces non-local moves for hard-core systems in a way which preserves micro-reversibility. Here we use this method to equilibrate a two-dimensional hard disc system far within its glassy phase. We show that indications of a thermodynamic transition are lacking up to very high densities, and that the glass is indistinguishable from the liquid on purely thermodynamic grounds.