Locally preferred structures and many-body static correlations in viscous liquids

TL;DR

This study explores how static many-body correlations influence the dynamics of glass-forming liquids, showing that locally preferred structures and their growth are key to understanding slow dynamics and fragility.

Contribution

It demonstrates the importance of including many-body static correlations and locally preferred structures in theories of the glass transition, especially for fragile glass-formers.

Findings

Growth of locally preferred structures signals slow dynamics onset

Truncating attractions reduces the spatial extension of correlated domains

Structural correlations correlate with the fragility of models

Abstract

We investigate the influence of static correlations beyond the pair level on the dynamics of selected model glass-formers. We compare the pair structure, angular distribution functions, and statistics of Voronoi polyhedra of two well-known Lennard-Jones mixtures as well as of the corresponding Weeks-Chandler-Andersen variants, in which the attractive part of the potential is truncated. By means of the Voronoi construction we identify the atomic arrangements corresponding to the locally preferred structures of the models. We find that the growth of domains formed by interconnected locally preferred structures signals the onset of the slow dynamics regime and allows to rationalize the different dynamic behaviors of the models. At low temperature, the spatial extension of the structurally correlated domains, evaluated at fixed relaxation time, increases with the fragility of the models and is systematically reduced by truncating the attractions. In view of these results, proper inclusion of many-body static correlations in theories of the glass transition appears crucial for the description of the dynamics of fragile glass-formers.