Showing papers by "Jens K. Nørskov published in 1984"

Interaction of deuterium with lattice defects in nickel

Abstract: The trapping of ion-implanted deuterium (D) in fee Ni is investigated by ion-beam-analysis techniques. Two lattice-defect traps have been observed with trap-binding enthalpies 0.24 eV and 0.43 eV referred to an untrapped solution site. The lattice location of D when associated with the defect traps is obtained by the channeling technique following anneals at various temperatures. The detailed analysis of these channeling data is based on a comparison with multirow continuum-model calculations of the angular yields for different D positions. These channeling calculations are extended by introducing a parameter δψ which encompasses the spreading in transverse energy caused by effects such as, for example, electron and nuclear multiple scattering. Also new and improved theoretical calculations based on the effective medium scheme of the equilibrium positions of H isotopes at defects, especially vacancies, are presented. The calculations show that D is delocalized over the entire vacancy, with a maximum density in the region between the vacancy and the nearest octahedral site. This picture is supported by the finding that the channeling data for D trapped to vacancies cannot be interpreted in terms of a single lattice site, and preference in site occupancy is found for D displaced from the vacancy towards the octahedral and (smaller) tetrahedral sites, respectively.