The Shapes of Cooperatively Rearranging Regions in Glass Forming Liquids

TL;DR

This paper investigates how the shapes of cooperatively rearranging regions in glass-forming liquids evolve from compact to fractal as temperature increases, using a microscopic theory aligned with experimental data.

Contribution

It provides a quantitative microscopic model within the random first order transition theory to describe the morphological change of rearranging regions in glasses.

Findings

Predicted correlation between crossover temperature ratio and heat capacity discontinuity.

Model agrees with experimental data for 21 materials.

Describes transition from compact to fractal regions near the dynamical crossover.

Abstract

The shapes of cooperatively rearranging regions in glassy liquids change from being compact at low temperatures to fractal or ``stringy'' as the dynamical crossover temperature from activated to collisional transport is approached from below. We present a quantitative microscopic treatment of this change of morphology within the framework of the random first order transition theory of glasses. We predict a correlation of the ratio of the dynamical crossover temperature to the laboratory glass transition temperature, and the heat capacity discontinuity at the glass transition, Delta C_p. The predicted correlation agrees with experimental results for the 21 materials compiled by Novikov and Sokolov.