Understanding fragility in supercooled Lennard-Jones mixtures. I. Locally preferred structures

TL;DR

This study uses molecular dynamics simulations to explore how local structural domains influence the fragility of supercooled Lennard-Jones mixtures, revealing that larger, slow domains correlate with increased fragility.

Contribution

It demonstrates a systematic link between local structural domain growth and fragility variations in supercooled Lennard-Jones mixtures.

Findings

Larger locally preferred structure domains form at lower temperatures.

Rapid growth of these domains correlates with higher fragility.

Fragility varies systematically with local structural organization.

Abstract

We reveal the existence of systematic variations of isobaric fragility in different supercooled Lennard-Jones binary mixtures by performing molecular dynamics simulations. The connection between fragility and local structures in the bulk is analyzed by means of a Voronoi construction. We find that clusters of particles belonging to locally preferred structures form slow, long-lived domains, whose spatial extension increases by decreasing temperature. As a general rule, a more rapid growth, upon supercooling, of such domains is associated to a more pronounced super-Arrhenius behavior, hence to a larger fragility.