Neutron scattering studies of γ-CoH

A powder sample of fcc (γ) cobalt hydride was synthesised under a pressure of 9 GPa and a temperature of 350 ° C and then studied at ambient pressure by neutron diffraction at 95 K and by inelastic neutron scattering (INS) at 5 K in the range of energy transfers 30-380 meV. A profile analysis of the neutron diffraction pattern showed that hydrogen occupies octahedral interstitial sites in the fcc metal lattice of γ-CoH with a=3.7124(5)  Å. The INS investigation demonstrated that the fundamental band of optical hydrogen vibrations consists of a strong peak at 102 meV with a broad shoulder towards higher energies. This intensity distribution is typical of hcp and fcc monohydrides of 3d- and 4d-metals, and the peak position as a function of the hydrogen-metal distance agrees with the dependence established for those hydrides earlier.