NMR second-moment study of hydrogen sites in icosahedral Ti₄₅Zr₃₈Ni₁₇ quasicrystals

Quasicrystalline Ti₄₅Zr₃₈Ni₁₇H_x samples were prepared with hydrogen-to-metal ratios (H/M) ranging from 0.25 to 1.85. The higher-concentration samples lost hydrogen, falling to H/M ≈ 1.6 over the course of days to weeks. The calibration of x-ray peak shifts as a measure of H/M, previously based on an extrapolation for H/M> 1.6, has been confirmed. Nuclear magnetic resonance measurements of the second moments (M₂) of the dipole-broadened ¹H line show the dependence on H/M expected for uniform filling of the quasicrystal with hydrogen. M₂ data were also consistent with canonical cell-tiling models of the host structure when hydrogen was sited preferentially near Ti or Zr neighbors. The quasicrystalline structure allows the chemical preference in hydrogen siting to be compatible with spatially uniform filling of the quasicrystal.