Hydrogen in Ti3Sb and Ti2Sb: Neutron vibrational spectroscopy and neutron diffraction studies

The structures of the Ti3SbHx(Dx) and Ti2SbH0.5(D0.5) hydrides and the vibrational spectra of H(D) atoms in these compounds have been studied by neutron diffraction and inelastic neutron scattering (INS). The analysis of the neutron diffraction data for Ti3SbD2.6 shows that D atoms occupy the tetrahedral interstitial 6d (Ti4) and 24k (Ti3Sb) sites of the A15-type host-metal lattice (space group Pm3¯n). H(D) atoms in Ti2SbH0.5 and Ti2SbD0.5 are found to occupy the octahedral interstitial 2b (Ti6) sites of the tetragonal host lattice (space group I4/mmm). The INS spectra for Ti3SbHx (x = 0.78 and 2.5) in the energy transfer range 50–200 meV are dominated by two peaks centered at 138 meV and 171 meV; these peaks can be attributed to vibrations of H atoms at 6d sites. The INS spectra for Ti2SbH0.5 and Ti2SbD0.5 are consistent with strongly anisotropic vibrations of H(D) atoms in the octahedral 2b sites.