Equilibration and aging of dense softsphere glassforming liquids
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The recently developed nonequilibrium extension of the selfconsistent generalized Langevin equation theory of irreversible relaxation is applied to the description of the irreversible process of equilibration and aging of a glassforming softsphere 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 nonequilibrium evolution of the static structure factor S(k;t) and of the dynamic properties, such as the selfintermediate scattering function F S(k,τ;t), where τ 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 αrelaxation time τα(t) as a function of t allows us to define the equilibration time teq(φ), as the time after which τα(t) has attained its equilibrium value ταeq(φ). It is predicted that both, teq(φ) and ταeq(φ), diverge as φ→φ(a), where φ(a) is the hardsphere dynamicarrest volume fraction φ(a)(≈0.582), thus suggesting that the measurement of equilibrium properties at and above φ(a ) is experimentally impossible. The theory also predicts that for fixed finite waiting times t, the plot of τα(t;φ) as a function of φ exhibits two regimes, corresponding to samples that have fully equilibrated within this waiting time (φ≤φ(c )(t)), and to samples for which equilibration is not yet complete (φ≥φ(c)(t)). The crossover volume fraction φ(c)(t) increases with t but saturates to the value φ(a). © 2013 American Physical Society.
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Equilibrium properties; Generalized Langevin equation theories; Glassforming liquid; Irreversible process; Particular condition; Scattering functions; Static structure factors; Temperature quench; Differential equations; Glass; Glass forming machines; Liquids; Spheres; Statistical mechanics; Constraint theory; solution and solubility; chemical model; chemical structure; chemistry; computer simulation; hardness; phase transition; solution and solubility; thermodynamics; Computer Simulation; Hardness; Models, Chemical; Models, Molecular; Phase Transition; Solutions; Thermodynamics
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