Nanoscale Structure and Structural Relaxation in ${\mathrm{Zr}}_{50}{\mathrm{Cu}}_{45}{\mathrm{Al}}_5$ Bulk Metallic Glass

Hybrid reverse Monte Carlo simulations of the structure of ${\mathrm{Zr}}_{50}{\mathrm{Cu}}_{45}{\mathrm{Al}}_5$ bulk metallic glass incorporating medium-range structure from fluctuation electron microscopy data and short-range structure from an embedded atom potential produce structures with significant fractions of icosahedral- and crystal-like atomic clusters. Similar clusters group together into nanometer-scale regions, and relaxation transforms crystal-like clusters into icosahedral clusters. A model refined against only the potential does not agree with the fluctuation microscopy data and contains few crystal-like clusters.

Figure 1

DSC data for as-quenched and annealed samples.

Figure 2

(a) Experimental $V(k)$ from the as-quenched and annealed samples and simulated $V(k)$ from the models. (b) Total x-ray $S(k)$ from experiment and calculated from the EAM-only and HRMC models, offset for clarity.

Figure 3

(a) Histograms of the VP categories for 15 the HRMC and EAM-only models. From top to bottom within each bar: Al-centered (green), Cu-centered (orange), and Zr-centered (gray) VPs. (b) CNA indices for the models. Error bars are the square root of the number of VPs or CNAs counted.

Figure 4

(a) A region including the crystal-like supercluster of the $300°\mathrm{C}$, 60 min annealed model. (b) A region of the EAM-only model the same size. The atoms are colored by the fraction of pentagons in their VPs. (c) CNA indices of the crystal-like supercluster and the remainder of the $300°\mathrm{C}$, 60 min annealed model. (d) A chain icosahedral supercluster from the yellow or upper circled region in (a). VP indices are shown for the central atoms, and atoms are colored by species.