Distorted icosahedral Ni5Nb3Zr5 clusters in the as-quenched and hydrogenated amorphous (Ni0.6Nb0.4)0.65Zr0.35 alloys

Local structures of the hydrogenated (Ni0.6Nb0.4)1-xZrx (x = 0.3–0.4) amorphous alloys attract much attention for the sake of their epoch-making electronic transport behaviors. We investigated the local structures by XAFS for the as-quenched (Ni0.6Nb0.4)0.65Zr0.35 and hydrogenated [(Ni0.6Nb0.4)0.65Zr0.35]0.922H0.078 amorphous alloys, in which ballistic conductivity has been observed. XAFS results of the Ni K-edge are analyzed based on the structure model deduced by the first principle calculation. The analysis suggests that highly distorted icosahedral Ni5Nb3Zr5 cluster, which has a centered-Ni and a surrounding Nb triangle, is a main structural unit of (Ni0.6Nb0.4)0.65Zr0.35 and the [(Ni0.6Nb0.4)0.65Zr0.35]0.922H0.078 amorphous alloys. This distorted icosahedral Ni5Nb3Zr5 cluster can be associated with the occurrence of the singular electronic transport behaviors of the hydrogenated (Ni0.6Nb0.4)0.65Zr0.35 alloy.