Finite size effects in the dynamics of glass-forming liquids

Abstract

We present a comprehensive theoretical study of finite size effects in the relaxation dynamics of glass-forming liquids. Our analysis is motivated by recent theoretical progress regarding the understanding of relevant correlation length scales in liquids approaching the glass transition. We obtain predictions both from general theoretical arguments and from a variety of specific perspectives: mode-coupling theory, kinetically constrained and defect models, and random first order transition theory. In the latter approach, we predict in particular a non-monotonic evolution of finite size effects across the mode-coupling crossover due to the competition between mode-coupling and activated relaxation. We study the role of competing relaxation mechanisms in giving rise to non-monotonic finite size effects by devising a kinetically constrained model where the proximity to the mode-coupling singularity can be continuously tuned by changing the lattice topology. We use our theoretical findings to interpret the results of extensive molecular dynamics studies of four model liquids with distinct structures and kinetic fragilities. While the less fragile model only displays modest finite size effects, we find a more significant size dependence evolving with temperature for more fragile models, such as Lennard-Jones particles and soft spheres. Finally, for a binary mixture of harmonic spheres we observe the predicted non-monotonic temperature evolution of finite size effects near the fitted mode-coupling singularity, suggesting that the crossover from mode-coupling to activated dynamics is more pronounced for this model. Finally, we discuss the close connection between our results and the recent report of a non-monotonic temperature evolution of a dynamic length scale near the mode-coupling crossover in harmonic spheres.

19 pages, 10 figures. V2: response to referees + refs added (close to published version)

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Cited by in corpus (10)

• Multiple length and time scales of dynamic heterogeneities in model glass-forming liquids: A systematic analysis of multi-point and multi-time correlations
• Decorrelation of the static and dynamic length scales in hard-sphere glass-formers
• Mean field theory of the swap Monte Carlo algorithm
• Geometrical Frustration and Static Correlations in Hard-Sphere Glass Formers
• Non-linear dynamic response of glass-forming liquids to random pinning
• The role of pair correlation function in the dynamical transition predicted by the mode coupling theory
• Relaxation dynamics in a binary hard-ellipse liquid
• Shear-stress fluctuations and relaxation in polymer glasses
• Enhanced diffusion in finite-size simulations of a fragile diatomic glass former
• Super-Cooled Liquids: Equivalence between Mode-Coupling Theory and Replica Approach