Inhomogeneity of local packing density and atomic bonding of Ni67Zr33 amorphous alloy

Highlights: • Inhomogeneous structural feature arising from dense and loose packing domains is observed. • The average size of dense packing domains is estimated to be 10–20 Å. • The dense packing domains are formed by strong atomic bonds and have thermodynamically stable structure. Pulsed neutron diffraction and synchrotron X-ray diffraction measurements were performed on a melt-quenching Ni₆₇Zr₃₃ amorphous alloy sample. The Ni-Ni, Ni-Zr and Zr-Zr nearest neighbour distributions were obtained from differences in the scattering intensities between the two probes in conjunction with the Gaussian fitting. The results demonstrate that the Ni-Zr and Zr-Zr nearest neighbour distributions are respectively represented by single Gaussian peaks but the Ni-Ni one is an asymmetric shape. Three-dimensional structure models were constructed by using reverse Monte Carlo (RMC) modelling method with fitting to the neutron and X-ray diffraction data sets. The Voronoi-Delaunay method was used on the RMC configurations to investigate the local packing properties of each coordination cluster. With reference to the macroscopic packing fraction, inhomogeneous structural feature arising from dense and loose packing domains is observed in the structure of Ni₆₇Zr₃₃ amorphous alloy.