Local Symmetry Effects in Actinide 4f X-ray Absorption in Oxides

Sergei M. Butorin; Anders Modin; Johan R. Vegelius; Michi To Suzuki; Peter M. Oppeneer; David A. Andersson; David K. Shuh

doi:10.1021/acs.analchem.5b04380

Local Symmetry Effects in Actinide 4f X-ray Absorption in Oxides

Sergei M. Butorin, Anders Modin, Johan R. Vegelius, Michi To Suzuki, Peter M. Oppeneer, David A. Andersson, David K. Shuh

IMR - Materials Design Division

Research output: Contribution to journal › Article › peer-review

11 Citations (Scopus)

Abstract

A systematic X-ray absorption study at actinide N_6,7 (4f → 6d transitions) edges was performed for light-actinide oxides including data obtained for the first time for NpO₂, PuO₂, and UO₃. The measurements were supported by ab initio calculations based on local-density-approximation with added 5f-5f Coulomb interaction (LDA+U). Improved energy resolution compared to common experiments at actinide L_2,3 (2p → 6d transitions) edges allowed us to resolve the major structures of the unoccupied 6d density of states (DOS) and estimate the crystal-field splittings in the 6d shell directly from the spectra of light-actinide dioxides. The measurements demonstrated an enhanced sensitivity of the N_6,7 spectral shape to changes in the compound crystal structure. For nonstoichiometric NpO_2-x, the filling of the entire band gap with Np 6d states was observed thus supporting a phase coexistence of Np metal and stoichiometric NpO₂ which is in agreement with the tentative Np-O phase diagram.

Original language	English
Pages (from-to)	4169-4173
Number of pages	5
Journal	Analytical Chemistry
Volume	88
Issue number	8
DOIs	https://doi.org/10.1021/acs.analchem.5b04380
Publication status	Published - 2016 May 3

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@article{51daa22a17c342b391100dd5cacf732f,

title = "Local Symmetry Effects in Actinide 4f X-ray Absorption in Oxides",

abstract = "A systematic X-ray absorption study at actinide N6,7 (4f → 6d transitions) edges was performed for light-actinide oxides including data obtained for the first time for NpO2, PuO2, and UO3. The measurements were supported by ab initio calculations based on local-density-approximation with added 5f-5f Coulomb interaction (LDA+U). Improved energy resolution compared to common experiments at actinide L2,3 (2p → 6d transitions) edges allowed us to resolve the major structures of the unoccupied 6d density of states (DOS) and estimate the crystal-field splittings in the 6d shell directly from the spectra of light-actinide dioxides. The measurements demonstrated an enhanced sensitivity of the N6,7 spectral shape to changes in the compound crystal structure. For nonstoichiometric NpO2-x, the filling of the entire band gap with Np 6d states was observed thus supporting a phase coexistence of Np metal and stoichiometric NpO2 which is in agreement with the tentative Np-O phase diagram.",

author = "Butorin, {Sergei M.} and Anders Modin and Vegelius, {Johan R.} and Suzuki, {Michi To} and Oppeneer, {Peter M.} and Andersson, {David A.} and Shuh, {David K.}",

note = "Funding Information: The work at the Advanced Light Source was supported by the Director, Office of Science, Office of Basic Energy Sciences, and this research (D.K.S.) was supported by the Director, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences Heavy Element Chemistry Program, both of the U.S. Department of Energy at Lawrence Berkeley National Laboratory under Contract No. DE-AC02-05CH11231. P.M.O. acknowledges support from the Swedish Research Council (VR), the European Atomic Energy Community's FP7-work programme (Grant No. 269903, {"}REDUPP{"}), and the Swedish National Infrastructure for Computing (SNIC). Publisher Copyright: {\textcopyright} 2016 American Chemical Society.",

year = "2016",

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doi = "10.1021/acs.analchem.5b04380",

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AU - Butorin, Sergei M.

AU - Modin, Anders

AU - Vegelius, Johan R.

AU - Suzuki, Michi To

AU - Oppeneer, Peter M.

AU - Andersson, David A.

AU - Shuh, David K.

N1 - Funding Information: The work at the Advanced Light Source was supported by the Director, Office of Science, Office of Basic Energy Sciences, and this research (D.K.S.) was supported by the Director, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences Heavy Element Chemistry Program, both of the U.S. Department of Energy at Lawrence Berkeley National Laboratory under Contract No. DE-AC02-05CH11231. P.M.O. acknowledges support from the Swedish Research Council (VR), the European Atomic Energy Community's FP7-work programme (Grant No. 269903, "REDUPP"), and the Swedish National Infrastructure for Computing (SNIC). Publisher Copyright: © 2016 American Chemical Society.

PY - 2016/5/3

Y1 - 2016/5/3

N2 - A systematic X-ray absorption study at actinide N6,7 (4f → 6d transitions) edges was performed for light-actinide oxides including data obtained for the first time for NpO2, PuO2, and UO3. The measurements were supported by ab initio calculations based on local-density-approximation with added 5f-5f Coulomb interaction (LDA+U). Improved energy resolution compared to common experiments at actinide L2,3 (2p → 6d transitions) edges allowed us to resolve the major structures of the unoccupied 6d density of states (DOS) and estimate the crystal-field splittings in the 6d shell directly from the spectra of light-actinide dioxides. The measurements demonstrated an enhanced sensitivity of the N6,7 spectral shape to changes in the compound crystal structure. For nonstoichiometric NpO2-x, the filling of the entire band gap with Np 6d states was observed thus supporting a phase coexistence of Np metal and stoichiometric NpO2 which is in agreement with the tentative Np-O phase diagram.

AB - A systematic X-ray absorption study at actinide N6,7 (4f → 6d transitions) edges was performed for light-actinide oxides including data obtained for the first time for NpO2, PuO2, and UO3. The measurements were supported by ab initio calculations based on local-density-approximation with added 5f-5f Coulomb interaction (LDA+U). Improved energy resolution compared to common experiments at actinide L2,3 (2p → 6d transitions) edges allowed us to resolve the major structures of the unoccupied 6d density of states (DOS) and estimate the crystal-field splittings in the 6d shell directly from the spectra of light-actinide dioxides. The measurements demonstrated an enhanced sensitivity of the N6,7 spectral shape to changes in the compound crystal structure. For nonstoichiometric NpO2-x, the filling of the entire band gap with Np 6d states was observed thus supporting a phase coexistence of Np metal and stoichiometric NpO2 which is in agreement with the tentative Np-O phase diagram.

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JO - Analytical Chemistry

JF - Analytical Chemistry

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Local Symmetry Effects in Actinide 4f X-ray Absorption in Oxides

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