title: 5 f -shell correlation effects in dioxides of light actinides studied by O 1s x-ray absorption and emission spectroscopies and first-principles calculations.
abstract: Soft x-ray emission and absorption spectroscopic data are reported for the O 1s region of a single crystal of UO2, a polycrystalline NpO2 sample, and a single crystal of PuO2. The experimental data are interpreted using first-principles correlated-electron calculations within the framework of the density functional theory with added Coulomb U interaction (DFT+U). A detailed analysis regarding the origin of different structures in the x-ray emission and x-ray absorption spectra is given and the effect of varying the intra-atomic Coulomb interaction-U for the 5 f electrons is investigated. Our data indicate that O 1s x-ray absorption and emission spectroscopies can, in combination with DFT+U calculations, successfully be used to study 5 f -shell Coulomb correlation effects in dioxides of light actinides. The values for the Coulomb U parameter in these dioxides are derived to be in the range of 4-5 eV.
authors.affiliation: Department of Physics and Astronomy, Uppsala University, PO Box 516, SE-751 20 Uppsala, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Modin
authors.forename: M-T
authors.initials: MT
authors.lastname: Suzuki
authors.forename: J
authors.initials: J
authors.lastname: Vegelius
authors.forename: Y
authors.initials: Y
authors.lastname: Yun
authors.forename: D K
authors.initials: DK
authors.lastname: Shuh
authors.forename: L
authors.initials: L
authors.lastname: Werme
authors.forename: J
authors.initials: J
authors.lastname: Nordgren
authors.forename: P M
authors.initials: PM
authors.lastname: Oppeneer
authors.forename: S M
authors.initials: SM
authors.lastname: Butorin