Anti-correlation between excitations and locally-favored structures in glass-forming systems

TL;DR

This study investigates the spatial relationship between excitations and locally favored structures in glass-forming systems, revealing a significant anti-correlation and spatial separation in deeply supercooled liquids through simulations and experiments.

Contribution

It provides the first detailed analysis of the spatial relationship between excitations and locally favored structures in glassformers, showing their anti-correlation in supercooled states.

Findings

Anti-correlation between excitations and LFS in supercooled liquids.

Spatial separation between excitations and LFS in deeply supercooled states.

LFS are well-packed and relatively stable structures.

Abstract

Dynamics that are microscopic in space and time, in which particles commit to a position, so-called excitations, are considered the elementary unit of relaxation in the Dynamic Facilitation (DF) theory of the glass transition. Meanwhile, geometric motifs known as locally favored structures (LFS) are associated with vitrification in many glassformers. Recent work indicates that the probability of particles found both in locally favored structures (LFS) and excitations decreases significantly upon supercooling suggesting that there is an anti-correlation between them [Ortlieb et al, Nature Commun. 14, 2621 (2023)]. However, the spatial relationship between excitations and LFS remains unclear. By employing state-of-the-art GPU computer simulations and colloid experiments, we analyze this relationship between LFS and excitations in model glassformers. We demonstrate that there is a spatial separation between the two in deeply supercooled liquids. This may be due to the fact that LFS are well-packed, thus they are relatively stable.