Site preference of cobalt and deuterium in the structure of a complex AB(5) alloy electrode - A neutron powder diffraction study

The site preference of cobalt and deuterium in the charged and discharged s tate of a commercial-type metal hydride anode was investigated by high reso lution neutron powder diffraction using an alloy with an altered isotope co mposition. in the alloy La(Ni-58(0.376) Ni-62(0.624))(3.55)Co0.75Mn0.33Al0. 30 the isotope ratio of Ni-58 to Ni-62 leads to a zero neutron scattering l ength for nickel. Rietveld refinement revealed that Al and Mn occupy the mi dplane 3g sites of the CaCu5 structure, while cobalt has a preference for 3 g but also occupies the basal plane 2c sites. The space group of the deuter ide remains P6/mmm which differs from the parent LaNi5D7 which is P6(3)mc. (C) 1999 The Electrochemical Society. S0013-4651(98)03-104-8. All rights re served.