Studies of Hydrogen Vibrations in Transition Metal Hydrides by Thermal Neutron Transmissions

Abstract

The total scattering cross sections of hydrogen atoms for thermal neutrons were measured as a function of the neutron energy for TiH _1.3 , TiH _1.6 , TiH _1.9 , TiH _2.0 , VH _0.25 , NbH _0.85 and TaH _0.7 at room temperature. The results clearly show the effect of the inelastic scattering of neutrons, due to excitation of the hydrogen vibrations, and are utilized to determine the energy levels of the optical vibrations in the hydride lattices. They are 0.135 eV for TiH _1.3-2.0 , 0.165 eV for VH _0.25 , 0.150 eV for NbH _0.85 , and 0.145 eV for TaH _0.7 . It was found that there is an approximately linear relation between the energies of the optical phonons and the metal-hydrogen distances reported on various hydrides, except for palladium hydride.