Equilibration and aging of dense soft-sphere glass-forming liquids

TL;DR

This paper applies a non-equilibrium theoretical framework to study the aging and equilibration processes in dense soft-sphere glass-forming liquids after a temperature quench, predicting diverging timescales near the arrest volume fraction.

Contribution

It extends the self-consistent generalized Langevin equation theory to non-equilibrium conditions, specifically modeling aging and equilibration in soft-sphere glasses after a quench.

Findings

Equilibration time diverges near the arrest volume fraction.

Predicted evolution of the alpha-relaxation time after a quench.

Equilibrium properties are experimentally inaccessible above the arrest volume fraction.

Abstract

The recently-developed non-equilibrium extension of the self-consistent generalized Langevin equation theory of irreversible relaxation [Phys. Rev. E (2010) 82, 061503; ibid. 061504] is applied to the description of the irreversible process of equilibration and aging of a glass-forming soft-sphere liquid that follows a sudden temperature quench, within the constraint that the local mean particle density remains uniform and constant. For these particular conditions, this theory describes the non-equilibrium evolution of the static structure factor S(k;t) and of the dynamic properties, such as the self-intermediate scattering function F_S(k,\tau;t), where tau is the correlation delay time and t is the evolution or waiting time after the quench. Specific predictions are presented, for the deepest quench (to zero temperature). The predicted evolution of the alpha-relaxation time \tau_\alpha(t) as a function of t allows us to define the equilibration time t^{eq}, as the time after which \tau_\alpha has attained its equilibrium value \tau_\alpha^{eq}. It is predicted that both, t^{eq}(\phi) and \tau_{\alpha}^{eq}, diverge as \phi \to \phi^{(a)}, where \phi^{(a)} is the hard-sphere dynamic-arrest volume fraction \phi^{(a)}\ (\approx 0.582), thus suggesting that the measurement of equilibrium properties at and above \phi^{(a)} is experimentally impossible.