A locally preferred structure characterises all dynamical regimes of a supercooled liquid

TL;DR

This paper reveals that a locally preferred icosahedral structure governs all dynamical regimes in supercooled liquids, linking structural cooperativity with key temperatures and glass formation through molecular dynamics simulations.

Contribution

It introduces a unified structural framework based on icosahedral domains to explain dynamical crossovers and glass transition in supercooled liquids.

Findings

High-temperature crossover at T_A linked to icosahedral domains

Supercooling leads to cooperative rearrangements and domain fluctuations

Domains stabilize and percolate before glass formation

Abstract

Recent experimental results suggest that metallic liquids universally exhibit a high-temperature dynamical crossover, which is correlated with the glass transition temperature ($T_{g}$). We demonstrate, using molecular dynamics results for Cu64Zr36, that this temperature, $T_{A} \approx 2 \times T_{g}$, is linked with cooperative atomic rearrangements that produce domains of connected icosahedra. Supercooling to a new characteristic temperature, $T_{D}$, is shown to produce higher order cooperative rearrangements amongst connected icosahedra, leading to large-scale domain fluctuations and the onset of glassy dynamics. These extensive domains then abruptly stabilize above $T_{g}$ and eventually percolate before the glass is formed. All characteristic temperatures ($T_{A}$, $T_{D}$ and $T_{g}$) are thus connected by successive manifestations of the structural cooperativity that begins at $T_{A}$.