Location and energy of interstitial hydrogen in the 1/1 approximant W-TiZrNi of the icosahedral TiZrNi quasicrystal: Rietveld refinement of x-ray and neutron diffraction data and density-functional calculations

Abstract

We present a determination of hydrogen sites in the 1/1 approximant structure of the icosahedral TiZrNi quasicrystal. A Rietveld refinement of neutron and x-ray diffraction data determines the locations of interstitial hydrogen atoms. Density-functional methods calculate the energy of hydrogen on all possible interstitial sites. The Rietveld refinement shows that the hydrogen atoms are preferentially located in the two lowest-energy sites. The filling of the remaining hydrogen sites is dominated by the repulsive hydrogen-hydrogen interaction at short distances.