Abstract
.In trajectory space, dynamical heterogeneities in glass-forming liquids correspond to the emergence of a dynamical phase transition between an active phase poor in local structure and an inactive phase which is rich in local structure. We support this scenario with the study of a model additive mixture of Lennard-Jones particles, quantifying how the choice of the relevant structural and dynamical observable affects the transition in trajectory space. We find that the low mobility, structure-rich phase is dominated by icosahedral order. Applying a non-equilibrium rheological protocol, we connect local order to the emergence of mechanical rigidity.Graphical abstract
Highlights
Supercooled liquids show emergent dynamical and structural heterogeneities when cooled towards the glass transition [1,2,3]
Dynamical heterogeneities in glass-forming liquids correspond to the emergence of a dynamical phase transition between an active phase poor in local structure and an inactive phase which is rich in local structure
The efficient filling of space with atoms of different sizes requires a certain degree of topological order [4] and the dynamic slowdown can rigorously be linked to emerging static lengthscales [5]; on the other hand, computer simulations have shown that the correlation between local structural features and slow dynamics is strongly model dependent [6,7]
Summary
Supercooled liquids show emergent dynamical and structural heterogeneities when cooled towards the glass transition [1,2,3]. The study of trajectory space in glassy systems has been originally promoted in the context of the dynamical facilitation theory of slow dynamics [33, 36, 37] Within this framework, on-lattice idealised models [36, 38,39,40] as well as more realistic models of structural glasses [33, 34, 41,42,43] have been shown to undergo a first-order dynamical phase transition in tra-. In the present numerical work, we consider the case of a popular atomistic glassformer originally introduced by Goran Wahnstrom as a simple model for supercooled liquids [47] It consists in a binary mixture of Lennard-Jones particles whose parametrization has been found to provide a good model of fragile glasses, with a strong coupling between its slow dynamics and the emergence of local geometrical motifs [7, 46, 48, 49]. The article is structured as follows: in sect. 2 we present the model studied and the importance sampling technique employed for trajectory sampling; in sect. 3 we introduce the relevant observables and the phase transitions in trajectory space that can be probed through the dynamical s-ensemble and the structural-dynamical μensemble; in sect. 4 we show that it is possible to connect the structural-dynamical transition to the emergence of rigidity in the glass, as the icosahedra-rich phase presents distinctive rheological properties; we conclude the article with an overview of the results and their implications
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