Frank-Kasper Z16 local structures in Cu-Zr metallic glasses

AKA Lu and K Nishio and T Morishita and K Ohara and Z Lu and A Hirata, PHYSICAL REVIEW B, 102, 184201 (2020).

DOI: 10.1103/PhysRevB.102.184201

Although previous molecular dynamics studies proposed the existence of Zr-centered Frank-Kasper Z16 structures in Cu-Zr metallic glasses, it cannot be concluded yet, owing to the degeneracy problem of the Voronoi index and the artifact in sets of potentials for Cu-Zr systems. We solve both problems by combining a recently developed Finnis-Sinclair potentials to generate realistic atomic structures and the p 3 code to properly differentiate local structures. In previous studies, the Voronoi index (0, 0, 12, 4) was typically associated with Frank-Kasper Z16 local structures. However, we demonstrate that this index includes two types of polyhedra, only one of which is associated with the Frank- Kasper Z16 structures. We reveal that the Z16 structures are more frequent than the other structures and that the two have different behaviors. The tendency of Zr-centered Z16 local structures to be neighbors of Cu-centered icosahedral local structures is also confirmed. Our findings illustrate the importance of properly differentiating local structures in order to elucidate the behavior of metallic glasses at the atomic scale.

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