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Open Access Publications from the University of California

Glassy Dynamics on a Lattice and in Nature

  • Author(s): Schuster, Kelsey Carle
  • Advisor(s): Chandler, David
  • et al.
Abstract

When a liquid is cooled below its melting temperature under conditions that prevent it from crystallizing, it forms an amorphous solid, or "glass." Glass-forming materials are ubiquitous, ranging from familiar silica glasses of which everyday windows are composed, to liquid water. While structurally indistinguishable from high-temperature liquids, supercooled liquids exhibit rich and complex dynamics. For instance, as the temperature is lowered, structural reorganization within supercooled liquids occurs over increasingly long time scales. Inspecting atomistic mobility over an interval of time reveals that dynamics is "heterogeneous," with distinct regions of mobility and immobility in space-time. In this dissertation, we characterize glassy dynamics in experimental systems and in coarse-grained lattice models. We show how the characteristic dynamics of atomistic glass-forming materials can be reproduced using a kinetically constrained lattice model referred to as the Arrow model, and thus present glassy dynamics "on a lattice." We then show that combining the Arrow model with a second lattice model that undergoes a thermodynamic phase transition captures the competition between crystallization and glass formation experienced by a material cooled below its melting temperature. With this combined model, we demonstrate how specific cooling protocols influence polycrystalline structure, and we qualitatively reproduce the non-monotonic temperature dependence of crystallization time scales. Finally, we explore glassy dynamics "in nature" by applying many of the same tools and ideas used to characterize glasses to study dynamical features of protein side-chains. We demonstrate the presence of supercooled liquid-like dynamics in a biomolecular system.

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