Anharmonicity of optical hydrogen vibrations in RhH

A polycrystalline sample of nearly stoichiometric fee rhodium hydride was synthesised under high hydrogen pressure and then studied at ambient pressure and 5 K by inelastic neutron scattering in the range of energy transfers 35-380 meV. The fundamental band of optical hydrogen vibrations was shown to consist of a strong peak centred at 74 meV and broadened towards higher energies. The second and third band demonstrated essentially anharmonic behaviour. which is not typical of monohydrides of 3d- and 4d-metals with close-packed metal lattices. (C) 2006 Elsevier B.V. All rights reserved.