The atomic packing in metallic glasses (MGs) is a long-standing issue. We investigate the atomic packing on different length scales for various MGs by X-ray diffraction and small-angle X-ray scattering techniques. Our findings are that (1) a noncubic power−law relationship exists between both normalized average basic volume (V a = M / (ρ × N), where N is the Avogadro constant and M and ρ are the molar mass and density of the sample, respectively) and the center of mass of the first four peaks (q i ) of structural factors in reciprocal space, having an exponent of about 2.52 ± 0.15 on the length scale of about 2.2−3.1 Å for 25 studied MGs, (2) a power−law relationship of the normalized scattering intensity vs q vector has an exponent of about 2.62 ± 0.12 on the length scale of about 250−785 Å for 5 studied MGs, and (3) in contrast, normalization of V a and r i (the center of mass of the first four peaks of pair correlation functions) in real space for 25 studied MGs reveals an exponent close to 3, similar to crystals. This discrepancy is elucidated by the fact that the pair correlation functions link with the atomic distribution along the radial direction but neglect how they are spatially packed on each shell. The perspective of the power−law relations on both length scales for the studied MGs deepens the understanding of the atomic packing structures in MGs.

Ab initio molecular dynamics simulations are performed to investigate the atomic structures and dynamics of NiZr and NiHf metallic liquids in a temperature range of 1400-2500 K. Calculated results are in good agreement with recently reported high temperature experimental data. Local atomic structures are analyzed and compared for NiZr and NiHf metallic liquids in terms of average bond length, coordination number, Honey-Andersen index, Bond-orientation order, spatial correlation and Voronoi tessellation methods. It is found that Zr-Zr bonds have larger average length of 3.32 Å than 3.22 Å for Hf-Hf bonds, causing sluggish diffusion in NiHf liquids. Zr and Hf atom-centered clusters with higher coordination numbers are inclined to aggregate with high-coordinated clusters, while Ni atom-centered clusters with lower coordination numbers prefer to avoiding to be the nearest neighbor with each other. Temperature dependent diffusion coefficients reveal the decoupled diffusion in both liquids, which are related with different spatial correlations for Ni- and Zr- (or Hf-) centered clusters.