Local structure of uranium in polycrystalline α-U2N3+δ film probed by X-ray absorption spectroscopy

Knowledge of the local structure such as U-N interaction is a prerequisite for a better understanding of the physical and chemical properties of nitrogen-rich uranium nitrides. The local structure of U in polycrystalline alpha-U2N3+delta film was investigated by using X-ray absorption spectroscopy at the U L-3 edge combined with spectral calculation using FEFF 9.6 program based on the ab initio multiple scattering theory. The polycrystalline alpha-U2N3+delta sample was shown to be close to U2N3 with a narrow distribution of U-N bond lengths. The average valence of U was estimated to be 1.3 and the average bond distance of U-N was determined to be 2.30 A. The local structure of U in the alpha-U2N3+delta sample can be further specifically expressed by a U2N3 model with a lattice parameter of 10.69 (9) A where U1 atoms are surrounded by nitrogen atoms at similar to 2.277, similar to 2.295 and similar to 2.320 A. (C) 2020 Elsevier B.V. All rights reserved.