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

The structural properties of the simulated $\rm Cu_αZr_{1-α}$ glassy alloys are studied in the wide range of the copper concentration $α$ 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 $α$ 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.