Irreversible equilibration and aging in glass-forming liquids

We review the recently-proposed non-equilibrium self-consistent generalized Langevin equation (NE-SCGLE) theory of irreversible processes in liquids, and describe the scenario that emerges from its application to the equilibration (or absence of equilibration!) of quenched glass-forming liquids. This theory extends to non-equilibrium conditions the SCGLE theory of dynamic arrest, which (just like the well-known mode coupling theory) determines the boundary of the ergodic domain of the system. In this first systematic application of the non-equilibrium theory we consider a model soft-sphere glass-forming liquid, initially at an ergodic equilibrium state, suddenly quenched to a lower final temperature that lies either (a) also in the ergodic domain, or (b) in the region of dynamically arrested states. In the first case the liquid will equilibrate within a finite equilibration time teq, while in the second the theory predicts that the liquid will age forever, (i.e., t eq = ∞). The dynamic arrest boundary is thus predicted to determine the crossover from equilibration to aging, and to be characterized by the divergence of the equilibration time. In either case the theory predicts the irreversible t-evolution of the measured static structure factor S(k;t) and of the dynamic properties such as the self-intermediate scattering function F S(k, τ;t). © 2013 American Institute of Physics.

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