Simulated Cu-Zr glassy alloys: the impact of composition on icosahedral order

TL;DR

This study investigates how copper concentration affects icosahedral order in Cu-Zr glassy alloys, revealing non-monotonic behavior and differences in cluster identification methods, which relate to glass-forming ability.

Contribution

It provides a detailed analysis of the composition-dependent icosahedral order in Cu-Zr alloys using two methods, highlighting non-monotonic trends and methodological discrepancies.

Findings

Icosahedral cluster abundance varies non-monotonically with composition.

Voronoi tessellation overestimates icosahedral clusters compared to bond orientational order.

Pinpoint compositions with high glass-forming ability are identified.

Abstract

The structural properties of the simulated $\rm Cu_{\alpha}Zr_{1-\alpha}$ glassy alloys are studied in the wide range of the copper concentration $\alpha$ to clarify the impact of the composition on the number density of the icosahedral clusters. Both bond orientational order parameters and Voronoi tessellation methods are used to identify these clusters. Our analysis shows that abundance of the icosahedral clusters and the chemical composition of these clusters are essentially non monotonic versus $\alpha$ and demonstrate local extrema. That qualitatively explains the existence of pinpoint compositions of high glass-forming ability observing in Cu-Zr alloys. Finally, it has been shown that Voronoi method overestimates drastically the abundance of the icosahedral clusters in comparison with the bond orientational order parameters one.