Cage-jump motion reveals universal dynamics and non-universal structural features in glass forming liquids

Abstract

The sluggish and heterogeneous dynamics of glass forming liquids is frequently associated to the transient coexistence of two phases of particles, respectively with an high and low mobility. In the absence of a dynamical order parameter that acquires a transient bimodal shape, these phases are commonly identified empirically, which makes difficult investigating their relation with the structural properties of the system. Here we show that the distribution of single particle diffusivities can be accessed within a Continuous Time Random Walk description of the intermittent motion, and that this distribution acquires a transient bimodal shape in the deeply supercooled regime, thus allowing for a clear identification of the two coexisting phase. In a simple two-dimensional glass forming model, the dynamic phase coexistence is accompanied by a striking structural counterpart: the distribution of the crystalline-like order parameter becomes also bimodal on cooling, with increasing overlap between ordered and immobile particles. This simple structural signature is absent in other models, such as the three-dimesional Kob-Andersen Lennard-Jones mixture, where more sophisticated order parameters might be relevant. In this perspective, the identification of the two dynamical coexisting phases opens the way to deeper investigations of structure-dynamics correlations.

Published in the J. Stat. Mech. Special Issue "The Role of Structure in Glassy and Jammed Systems"

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• Structural-dynamical transition in the Wahnström mixture
• Emergence and percolation of rigid domains during colloidal glass transition
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• Glassy phases of the Gaussian Core Model
• Concentrated suspensions of Brownian beads in water: dynamic heterogeneities trough a simple experimental technique
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• Dynamics of dense hard sphere colloidal systems: a numerical analysis
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