EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Metallic glasses (MGs) are amorphous solids which lack long-range, but exhibiting significant degree of short-range order. The local atomic structure of MGs can be reversibly modified by an external load but the actual atomic-level mechanism of elastic deformation of amorphous metals is not well understood. In this work, we applied molecular dynamics (MD) simulations and density functional theory (DFT) calculations to study the relation between the atomic and the electronic structures of selected binary Zr-Cu metallic glasses in a wide range of hydrostatic pressure reaching 100 GPa.
We found that the most characteristic structural motif in Zr-Cu MGs is a Cu-centered icosahedral cluster. The frequency of occurrence of those clusters was found to be increasing with pressure1. The variations in the short-range order on compression are due mostly to Zr atoms, since pressure is accommodated mainly by compressing of relatively soft Zr-Zr pairs. Previous works2 on Zr-Cu MGs revealed an unexpected splitting of the distribution of Zr-Zr distances for pressures exceeding 50 GPa. In this study, we attribute this phenomenon to pressure-induced modifications of the electronic structure of Zr atoms. Recent studies demonstrate that electronegativity of the atoms changes under pressure3. In particular, the electronegativity of Zr drops around 50 GPa. Our DFT studies of 54 atoms supercell extracted from the MD simulation show a significant change in bonding type - from mostly metallic at low pressure to covalent-like bonding in the high-pressure. Moreover, we applied the Löwdin population analysis to assess the direction of the pressure-induced charge transfer - from Cu to Zr and the redistribution in the electronic structure of Zr atoms.

1. Dziegielewski, P. High Press. Res. (2020).
2. Sengul, S. Comput. Mater. Sci. (2020).
3. Rahm, M. J. Am. Chem. Soc. (2019).