Neutron diffraction studies of hafnium–hydrogen and titanium–hydrogen systems

Abstract

Results of neutron and X-ray diffraction studies on I-If and Ti hydrogen systems are reported. It is shown that the first single-phase hydride formed is a non-stoichiometric compound with a CaF2-type structure. It deforms to a face-centered tetragonal structure as the composition approaches MX 2. From the crystal-structure data of these hydrides the positions of hydrogen atoms, the nearest-neighbor atoms and their interatomic distances are determined. It is indicated that the size of the 'hole' for the hydrogen atom in the hydride is such that it must enter as an ion. The effect of metal-hydrogen bonds on the physical properties of hydrides, such as characteristic temperature and vibration frequency, is given. Evidence and explanation for the embrittlement of metals by hydrogen are offered.