(451f) A Theory of Localized Excitations in Supercooled Liquids
AIChE Annual Meeting
2021
2021 Annual Meeting
Engineering Sciences and Fundamentals
Thermophysical Properties: Theory and Experiments for Charged Systems
Wednesday, November 10, 2021 - 9:20am to 9:36am
The microscopic motion of glass-forming liquids dramatically slows down with decreasing temperature. This slowdown is accompanied by dynamical heterogeneity where localized regions of particle mobility and extended immobile regions emerge from the liquid. There are two competing perspectives to explain these phenomena. One perspective proposes that the structural/static properties of the liquid can be used to explain the slow down in dynamics. Another perspective, such as dynamical facilitation (DF) theory, proposes that dynamics are driven by emergent excitations whose origins were believed to be independent of liquid structure. These excitations can then facilitate the creation and relaxation of nearby excitations. DF theory is very successful in predicting many key properties of glassy dynamics including, relaxation behaviors of single- and multi-component systems, temperature-dependence of heat capacities, breakdown of Stokes-Einstein diffusion, and the competing dynamics of crystallization and vitrification. However, two important and fundamental questions still need to be answered in DF theory: (1) what is the origin of excitations? and (2) why do excitations facilitate the relaxation and creation of nearby excitations?
Our work [1] shows that the origin of excitations lies, in fact, within the structure by constructing a theory where excitations correspond to localized regions of pure shear emerging from the liquid. Inside the localized zone, a bond-breaking event occurs in the form of a T1 transition which then re-organizes the local structure. The energy barrier to form such excitations can be predicted from the knowledge of structure and elasticity inherent within the liquid. We compared the prediction of our theory to that of DF theory where good quantitative agreement is found across six model glass formers with continuous poly-dispersity. These results demonstrate the applicability of our theory to a wide range of glass formers including dense colloidal suspensions and metallic glassy alloys.
[1] M. R. Hasyim, and K. K. Mandadapu. "A Theory of Localized Excitations in Supercooled Liquids." arXiv preprint arXiv:2103.03015 (2021).
Our work [1] shows that the origin of excitations lies, in fact, within the structure by constructing a theory where excitations correspond to localized regions of pure shear emerging from the liquid. Inside the localized zone, a bond-breaking event occurs in the form of a T1 transition which then re-organizes the local structure. The energy barrier to form such excitations can be predicted from the knowledge of structure and elasticity inherent within the liquid. We compared the prediction of our theory to that of DF theory where good quantitative agreement is found across six model glass formers with continuous poly-dispersity. These results demonstrate the applicability of our theory to a wide range of glass formers including dense colloidal suspensions and metallic glassy alloys.
[1] M. R. Hasyim, and K. K. Mandadapu. "A Theory of Localized Excitations in Supercooled Liquids." arXiv preprint arXiv:2103.03015 (2021).