X-ray absorption fine structure spectroscopic study of uranium nitrides

Abstract

Uranium mononitride (UN), sesquinitride (U₂N₃) and dinitride (UN₂) were characterized by extended X-Ray absorption fine structure spectroscopy. Analysis on UN indicate the presence of three uranium shells at distances of 3.46(3), 4.89(5) and 6.01(6) Å and a nitrogen shell at a distance of 2.46(2) Å. For U₂N₃, two absorbing uranium atoms at different crystallographic positions are present in the structure. One of the uranium atoms is surrounded by nitrogen atoms at 2.28(2) Å and by uranium atoms at 3.66(4) and 3.95(4) Å. The second type of uranium atom is surrounded by nitrogen atoms at 2.33(2) and 2.64(3) Å and by uranium atoms at 3.66(4), 3.95(4) and 5.31(5) Å. Results on UN₂ indicate two uranium shells at 3.71(4) and 5.32(5) Å and two nitrogen shells at 2.28(2) and 4.34(4) Å. The lattice parameters of UN, U₂N₃ and UN₂ unit cells were respectively determined to be 4.89(5), 10.62(10) and 5.32(5) Å. Those results are well in agreement with those obtained by X-Ray diffraction analysis.