title: Structural Properties and Charge Distribution of the Sodium Uranium, Neptunium, and Plutonium Ternary Oxides: A Combined X-ray Diffraction and XANES Study.
abstract: The charge distributions in α-Na2UO4, Na3NpO4, α-Na2NpO4, Na4NpO5, Na5NpO6, Na2PuO3, Na4PuO5, and Na5PuO6 are investigated in this work using X-ray absorption near-edge structure (XANES) spectroscopy at the U-L3, Np-L3, and Pu-L3 edges. In addition, a Rietveld refinement of monoclinic Na2PuO3, in space group C2/c, is reported for the first time, and the existence of the isostructural Na2NpO3 phase is revealed. In contrast to measurements in solution, the number of published XANES data for neptunium and plutonium solid phases with a valence state higher than IV is very limited. The present results cover a wide range of oxidation states, namely, IV to VII, and can serve as reference for future investigations. The sodium actinide series show a variety of local coordination geometries, and correlations between the shape of the XANES spectra and the local structural environments are discussed herein.
authors.affiliation: European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU) , P.O. Box 2340, D-76125 Karlsruhe, Germany.|Department of Materials Science and Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom.
authors.forename: Anna L
authors.initials: AL
authors.lastname: Smith
authors.affiliation: CEA, DEN, DEC, CEN Cadarache, 13108 St. Paul Lez Durance, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Martin
authors.affiliation: European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU) , P.O. Box 2340, D-76125 Karlsruhe, Germany.
authors.forename: Damien
authors.initials: D
authors.lastname: Prieur
authors.affiliation: Helmholtz Zentrum Dresden Rossendorf (HZDR), Institute of Resource Ecology , P.O. Box 10119, 01314 Dresden, Germany.
authors.forename: Andreas C
authors.initials: AC
authors.lastname: Scheinost
authors.affiliation: European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU) , P.O. Box 2340, D-76125 Karlsruhe, Germany.
authors.forename: Philippe E
authors.initials: PE
authors.lastname: Raison
authors.affiliation: Department of Materials Science and Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom.
authors.forename: Anthony K
authors.initials: AK
authors.lastname: Cheetham
authors.affiliation: European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU) , P.O. Box 2340, D-76125 Karlsruhe, Germany.
authors.forename: Rudy J M
authors.initials: RJ
authors.lastname: Konings