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

详细信息    查看全文

• 作者：Sergei M. Butorin ; Anders Modin ; Johan R. Vegelius ; Michi-To Suzuki ; Peter M. Oppeneer ; David A. Andersson ; David K. Shuh
• 刊名：Analytical Chemistry
• 出版年：2016
• 出版时间：April 19, 2016
• 年：2016
• 卷：88
• 期：8
• 页码：4169-4173
• 全文大小：343K
• 年卷期：0
• ISSN：1520-6882

文摘

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.