立方U2N3中极性铀八极子的案例
A case for polar uranium octupoles in cubic U2N3
AI总结：
本研究通过对比共振X射线衍射数据与对称性计算，论证立方U2N3中非中心对称位点存在高阶极性铀多极子，并以禁戒布拉格斑点作为关键证据。
摘要：
根据常规X射线衍射图谱[R. Troć, J. Solid State Chem. 13, 14 (1975)]，倍半氮化物α-U2N3中的铀离子占据独立的非中心对称和中心对称位点。我们认为，在Lawrence Bright等人最近发表的共振X射线衍射数据[Phys. Rev. B 100, 134426 (2019)]中揭示了非中心对称位点中的极性铀多极子。为此，将其在铀M4吸收边附近初级X射线能量下收集的衍射数据与针对方铁锰矿α-Mn2O3晶格结构计算的对称性感知衍射振幅进行比较。在该晶格衍射图谱中被禁止的布拉格斑点似乎为高阶极性铀多极子提供了明确证据。
英文摘要：
Uranium ions in sesquinitride alpha-U2N3 occupy independent acentric and centrosymmetric sites according to conventional x-ray diffraction patterns [R. Troć, J. Solid State Chem. 13, 14 (1975)]. We submit that polar uranium multipoles in acentric sites are revealed in resonant x-ray diffraction data recently published by Lawrence Bright et al. [Phys. Rev. B 100, 134426 (2019)]. To this end, their diffraction data gathered with a primary x-ray energy in the vicinity of the uranium M4 absorption edge are compared to symmetry-informed diffraction amplitudes calculated for the bixbyite alpha-Mn2O3 lattice structure. Bragg spots forbidden in this lattice diffraction pattern appear to provide clear-cut evidence for high-order polar uranium multipoles.
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