Critical scaling of icosahedral medium-range order in CuZr metallic glass-forming liquids

TL;DR

This study uses molecular dynamics simulations and scaling analysis to reveal critical behavior and structural phase transition in icosahedral medium-range order in CuZr metallic glasses, linking structure to glass transition dynamics.

Contribution

It demonstrates critical scaling laws and a potential structural phase transition in medium-range order, advancing understanding of glass transition mechanisms in metallic glasses.

Findings

Cluster size distribution follows a scaling law with temperature.

Percolation of icosahedral structures suggests a structural phase transition.

Enhanced medium-range order lowers energy and causes dynamic slowdown.

Abstract

The temperature evolution of icosahedral medium-range order formed by interpenetrating icosahedra in CuZr metallic glass-forming liquids was investigated via molecular dynamics simulations. Scaling analysis based on percolation theory was employed, and it is found that the size distribution of clusters formed by the central atoms of icosahedra at various temperatures follows a very good scaling law with the cluster number density scaled by $S^{-\tau}$ and the cluster size $S$ scaled by $|1-T_c/T|^{-1/\sigma}$, respectively. Here $T_c$ is scaling crossover-temperature. $\tau$ and $\sigma$ are scaling exponents. The critical scaling behaviour suggests that there would be a structural phase transition manifested by percolation of locally favoured structures underlying the glass transition, if the liquid could be cooled slowly enough but without crystallization intervening. Furthermore, it is revealed that when icosahedral short-range order (ISRO) extends to medium-range length scale by connection, the atomic configurations of ISROs will be optimized from distorted ones towards more regular ones gradually, which significantly lowers the energies of ISROs and introduces geometric frustration simultaneously. Both factors make key impacts on the drastic dynamic slowdown of supercooled liquids. Our findings provide direct structure-property relationship for understanding the nature of glass transition.