Connectivity of icosahedral network and a dramatically growing static length scale in Cu-Zr binary metallic glasses

Abstract

We report on and characterize, via molecular dynamics studies, the evolution of the structure of Cu${}_{50}$Zr${}_{50}$ and Cu${}_{64}$Zr${}_{36}$ metallic glasses (MGs) as temperature is varied. Interestingly, a percolating icosahedral network appears in the Cu${}_{64}$Zr${}_{36}$ 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, noninterpenetrating 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 noninterpenetrating connections for facilitating extensive structural networks in Cu-Zr MGs, which in turn drive dynamical slowing in these materials.