A Theory of Localized Excitations in Supercooled Liquids

Abstract

A new connection between structure and dynamics in glass-forming liquids is presented. We show how the origin of spatially localized excitations, as defined by dynamical facilitation (DF) theory, can be understood from a structure-based framework. This framework is constructed by associating excitation events in DF theory to hopping events between energy minima in the potential energy landscape (PEL). By reducing the PEL to an equal energy well picture and applying a harmonic approximation, we develop a field theory to describe elastic fluctuations about inherent states, which are energy minimizing configurations of the PEL. We model an excitation as a shear transformation zone (STZ) inducing a localized pure shear deformation onto an inherent state. We connect STZs to T1 transition events that break the elastic bonds holding the local structure of an inherent state. A formula for the excitation energy barrier, denoted as $J_{\sigma }$, is obtained as a function of inherent-state elastic moduli and radial distribution function. The energy barrier from the current theory is compared to one predicted by the DF theory where good agreement is found in various two-dimensional continuous poly-disperse atomistic models of glass formers. These results strengthen the role of structure and elasticity in driving glassy dynamics through the creation and relaxation of localized excitations.

11 pages, 6 figures, 1 table; final version submitted to the Journal of Chemical Physics

References in corpus (4)

• Glassy dynamics of kinetically constrained models
• Irreversible reorganization in a supercooled liquid originates from localised soft modes
• Ergodicity and Slowing Down in Glass-Forming Systems with Soft Potentials: No Finite-Temperature Singularities
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• Scaling Description of Dynamical Heterogeneity and Avalanches of Relaxation in Glass-Forming Liquids
• Direct numerical analysis of dynamic facilitation in glass-forming liquids
• Supervised Learning and the Finite-Temperature String Method for Computing Committor Functions and Reaction Rates
• Boundary conditions dependence of the phase transition in the quantum Newman-Moore model
• Inherent-State Melting and the Onset of Glassy Dynamics in Two-Dimensional Supercooled Liquids
• Modeling non-linear dielectric susceptibilities of supercooled molecular liquids
• Does mesoscopic elasticity control viscous slowing down in glassforming liquids?