Liquid elasticity length, universal dynamic crossovers and glass transition

TL;DR

This paper introduces the concept of liquid elasticity length to explain universal dynamic crossovers in liquids, linking them to relaxation times and system size, and verifies a prediction about viscosity increase with system size through experiments.

Contribution

It proposes a new framework based on liquid elasticity length to unify understanding of dynamic crossovers and the glass transition, connecting microscopic and macroscopic properties.

Findings

Identification of two universal dynamic crossovers at specific relaxation times.

Introduction of liquid elasticity length as a key parameter in liquid dynamics.

Experimental verification that viscosity increases with system size in honey.

Abstract

We discuss two main universal dynamic crossovers in a liquid that correspond to relaxation times of 1 ps and 10^{-7}--10^{-6} s. We introduce the concept of liquid elasticity length $d_{\rm el}$. At room temperature, $d_{\rm el}$ is several \AA in water and increases to 0.01 mm in honey and 1 mm in tar. We discuss that on temperature decrease, $d_{\rm el}=d_{\rm m}$ and $d_{\rm el}=L$ correspond to the two dynamic crossovers, where $d_{\rm m}$ is the medium-range order and L is system size. The second crossover defines all kinetic aspects of the glass transition whereas ``thermodynamic'' glass transition is realized in the limit of infinite system size only. One prediction of this picture is the increase of viscosity with the size of macroscopic system, which we verify by measuring the viscosity of honey.