Common mechanism of thermodynamic and mechanical origin for ageing and crystallisation of glasses

Taiki Yanagishima; John Russo; Hajime Tanaka

doi:10.1038/ncomms15954

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arXiv · 1708.00579

Common mechanism of thermodynamic and mechanical origin for ageing and crystallisation of glasses

Taiki Yanagishima·John Russo·Hajime Tanaka

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Abstract

The glassy state is known to undergo slow structural relaxation, where the system progressively explores lower free-energy minima which are either amorphous (ageing) or crystalline (devitrification). Recently, there is growing interest in the unusual intermittent collective displacements of a large number of particles known as "avalanches". However, their structural origin and dynamics are yet to be fully addressed. Here, we study hard-sphere glasses which either crystallise or age depending on the degree of size polydispersity, and show that a small number of particles are thermodynamically driven to rearrange in regions of low density and bond orientational order. This causes a transient loss of mechanical equilibrium which facilitates a large cascade of motion. Combined with previously identified phenomenology, we have a complete kinetic pathway for structural change which is common to both ageing and crystallisation. Furthermore, this suggests that transient force balance is what distinguishes glasses from supercooled liquids.

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Taiki Yanagishima, John Russo, Hajime Tanaka. 2017-08-02. Common mechanism of thermodynamic and mechanical origin for ageing and crystallisation of glasses. https://doi.org/10.1038/ncomms15954

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