The effect of Mo addition on structure and glass forming ability of Ni-Zr alloys

The classical molecular dynamics simulation was conducted to investigate the effect of Mo atom addition upon the atomic structure and glass-forming ability of Ni₆₄Zr_36-xMo_x (x = 0, 6, 12, 18, 21, 24, 27) metallic glasses (MGs), in terms of the system energy, pair distribution functions (PDFs), and the largest standard cluster analysis. It is found that Mo atoms do not simply replace Zr atoms, but remarkably change the atomic and chemical order; resulting in a more stable, more compact and more complex structures indicated by the split of the first major peak on PDF curves. The addition of Mo atoms does not favor the formation of icosahedrons but enhances the topologically close-packed (TCP) structures that are not only responsible for the split of the first major peak on the PDF curves, but also positively correlation with the GFA predicted by formation enthalpy. Thus, as a superset of icosahedrons, TCP structures are one of the essential characteristic of MGs and significantly enhances the GFA of Ni₆₄Zr_36-xMo_x ternary glass metals. These findings shed a new light on the understanding of the structure and the structure-GFA relationship of MGs.