Theoretical and experimental investigation of the electronic structure of Ti-Zr-Ni and Ti-Zr-Ni:H alloys

We have calculated the band structure of a model 1/1 approximant of cubic Frank-Kasper type structure of the icosahedral Ti-Zr-Ni quasicrystal. We have shown that the electronic structure is dominated by the metals d bands with a complete mixing of Ti and Zr states. With respect to the pure metal, Ni d states appear to be strongly modified upon alloying. The experimental investigation of the icosahedral alloy shows good agreement with the theoretical calculations for the approximant. We have shown experimentally that dramatic modifications of both occupied and unoccupied states occur in the hydrogenated quasicrystal, due to bonding to H. We have asserted preferential Zr-H rather than Ni-H bonding. We have suggested that Ti-H bonding should also be significant. We interpret the high H/metal ratio by the fact that H bonds to each of the elements in the quasicrystal.