Connectivity of the Icosahedral Network and a Dramatically Growing Static Length Scale in Cu-Zr Binary Metallic Glasses

TL;DR

This study uses molecular dynamics to reveal how icosahedral networks form and grow in Cu-Zr metallic glasses as they cool, significantly influencing their structural and dynamical properties.

Contribution

It introduces a static length scale related to icosahedral connectivity that dramatically increases near the glass transition in Cu-Zr MGs.

Findings

Percolating icosahedral networks form in Cu64Zr36 during supercooling.

Non-interpenetrating icosahedral connections become dominant upon supercooling.

The growth of the static length scale correlates with dynamical slowing in the material.

Abstract

We report on and characterize, via molecular dynamics (MD) studies, the evolution of the structure of Cu50Zr50 and Cu64Zr36 metallic glasses (MGs) as temperature is varied. Interestingly, a percolating icosahedral network appears in the Cu64Zr36 system as it is supercooled. This leads us to introduce a static length scale, which grows dramatically as this three dimensional system approaches the glass transition. Amidst interpenetrating connections, non-interpenetrating connections between icosahedra are shown to become prevalent upon supercooling and to greatly enhance the connectivity of the MG's icosahedral network. Additionally, we characterize the chemical compositions of the icosahedral networks and their components. These findings demonstrate the importance of non-interpenetrating connections for facilitating extensive structural networks in Cu-Zr MGs, which in turn drive dynamical slowing in these materials.