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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Solution and refinement of the crystal structure of Bi7Ta3O18
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Solution and refinement of the crystal structure of Bi7Ta3O18

机译：Bi7Ta3O18晶体结构的求解和精细化

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摘要

The structure of heptabismuth tritantalum octadecaoxide, Bi7Ta3O18, has been solved and refined using single-crystal X-ray diffraction data collected at a synchrotron source in conjunction with unit-cell and symmetry information derived from electron diffraction. The space-group symmetry is triclinic C1 but is very close to monoclinic C2/m. A twin component observed during data collection was successfully modelled in the refinement. The C2/m prototype fitted all the Rietveld-refinable features of a medium-resolution neutron powder diffraction pattern. The metal-atom array is approximately face-centred cubic (fluorite type), punctuated by regularly spaced displacement faults perpendicular to the [111](fluorite) direction every 2.5 fluorite unit cells. The metal-atom populations and O-atom positions are fully ordered. The Ta5+ cations are octahedrally coordinated, with TaO6 octahedra forming columns. The remaining O atoms occupy distorted fluorite positions. The Bi3+ cations occupy octahedral, square pyramidal or trigonal prismatic sites within the O-atom array; strain in the latter coordination environment appears to be responsible for the lowering of symmetry from monoclinic to triclinic. [References: 16]
机译：已使用在同步加速器源处收集的单晶X射线衍射数据，结合了从电子衍射获得的晶胞和对称性信息，对八氧化三庚钽的结构Bi7Ta3O18进行了解析和改进。空间群的对称性是三斜C1，但非常接近单斜C2 / m。数据收集过程中观察到的孪生成分已成功地进行了建模。 C2 / m原型符合中分辨率中子粉末衍射图的所有Rietveld可精修特征。金属原子阵列大约是面心立方（萤石类型），每2.5个萤石晶胞被垂直于[111]（萤石）方向的规则间隔的位移断层打断。金属原子总数和O原子位置是完全有序的。 Ta5 +阳离子是八面体配位的，TaO6八面体形成柱。其余的O原子占据变形的萤石位置。 Bi3 +阳离子占据O原子阵列中的八面体，方形金字塔形或三角形棱柱形位点;后者协调环境中的应变似乎是造成单斜向三斜对称性降低的原因。 [参考：16]

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