Title: A model of heterogeneous undercooled liquid and glass accounting for temperature-dependent nonexponentiality and enthalpy fluctuation
Abstract: Glasses are nonequilibrium systems that exhibit dynamic changes in their properties, such as density and enthalpy, over time and with variations in temperature. This phenomenon is referred to as the structural relaxation of glass. Predicting the structural relaxation presents a significant challenge due to the intricate dynamics, characterized by three ‘non’ attributes: 1) nonlinearity, 2) non-Arrhenius behavior, and 3) nonexponential kinetics. The nonlinearity arises as a consequence of the nonequilibrium nature inherent to glasses, and it can be parameterized by the fictive temperature, which represents the nonequilibrium state. Both the non-Arrhenius behavior and nonexponential kinetics stem from the spatial heterogeneity of density and enthalpy within undercooled liquids and glasses. Thus, spatial heterogeneity plays a pivotal role in understanding the structural relaxation. Conventional phenomenological models often fail to fully capture this phenomenon. In this presentation, we propose a model that incorporates spatial heterogeneity to describe both undercooled liquids and glasses. We extend the existing structural relaxation model by introducing the distribution of equilibrium fictive temperature (). This model is applied to various organic and inorganic systems, and the simulated results are compared with experimental measurements. Further, the initial results of the application to the planetary ball milled Na-P-S glasses fabricated at the Martin’s Lab are also shown.
Bio: Wataru Takeda is a Ph.D. candidate in the Materials Science and Engineering department at the University of Arizona. He earned his Bachelor of Arts in Physics from Coe College. Wataru is currently conducting research at Lucas’ Lab, where he focuses on understanding the thermodynamic and kinetic behavior of chalcogenide-based glasses through a combination of experimental techniques and modeling approaches. He has co-authored two peer-reviewed publications in the Journal of Chemical Physics. In his free time, he enjoys watching soccer and practicing Judo.
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