Testing theories of the glass transition with the same liquid, but many kinetic rules

TL;DR

This study investigates how varying kinetic rules in super-cooled liquids affect the glass transition, revealing that transition location depends linearly on these rules and that dynamical heterogeneities are independent of static structure.

Contribution

It introduces a broad class of kinetic rules, including swap moves and restricted directions, to test their impact on the glass transition, challenging existing theories based on static structure.

Findings

Glass transition location varies smoothly with kinetic rule parameters.

Transition point is governed by a linear combination of kinetic rule fractions.

Dynamical heterogeneities are similar across different kinetic rules at the transition.

Abstract

We study the glass transition by exploring a broad class of kinetic rules that can significantly modify the normal dynamics of super-cooled liquids, while maintaining thermal equilibrium. Beyond the usual dynamics of liquids, this class includes dynamics in which a fraction $(1-f_R)$ of the particles can perform pairwise exchange or 'swap moves', while a fraction $f_P$ of the particles can only move along restricted directions. We find that (i) the location of the glass transition varies greatly but smoothly as $f_P$ and $f_R$ change and (ii) it is governed by a linear combination of $f_P$ and $f_R$. (iii) Dynamical heterogeneities are not governed by the static structure of the material. Instead, they are similar at the glass transition across the ($f_R$, $f_P$) diagram. These observations are negative items for some existing theories of the glass transition, particularly those reliant on growing thermodynamic order or locally favored structure, and open new avenues to test other approaches.