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首页> 外文期刊>Acta Crystallographica, Section B. Structural science, crystal engineering and materials >Structure of russellite (Bi_2WO_6): origin of ferroelectricity and the effect of the stereoactive lone electron pair on the structure
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Structure of russellite (Bi_2WO_6): origin of ferroelectricity and the effect of the stereoactive lone electron pair on the structure

机译：罗素石结构（BI_2WO_6）：铁电的来源和立体活性孤电子对对结构的影响

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摘要

The structure of the low-temperature polar (orthorhombic) phase of russellite (Bi_2WO_6) was examined on artificial specimens with precise single-crystal X-ray diffraction experiments. The final atomic arrangement thus obtained was identical to that reported by Knight [Miner. Mag. (1992), 56, 399-409] with powder neutron diffraction. The residual density attributable to a stereochemically- active lone pair of electrons of bismuth was prominent at approximately the centre of a larger cap of BiO_8 square antiprisms, that is on the line from the Bi sites to an adjacent WO_4~(2-) slab along the b-axis direction. Quite uneven Bi-O distances and the formation of a vacant coordination hemisphere (within 3 ?) should, therefore, be ascribed to the strong demand of bismuth to form shorter Bi-O bonds to use up its electrostatic charge within its coordination environment. The shift of bismuth along -c propagates via the correlated shift of the W site and these cooperative shifts cause ferroelectricity in the compound. This propagation was easily effected by the intrusion of molecules such as acetone into the structure.
机译：在具有精确单晶X射线衍射实验的人工标本上检查了russellite（bi_2wo_6）的低温极性（正交）阶段的结构。由此获得的最终原子布置与骑士报告的相同[矿工。梅。 （1992），56,399-409]粉末中子衍射。归属于立体化学 - 活性的孤独的铋电子的残余密度在大致的Bio_8平方抗厌曲帽的中心突出，即在Bi位点到相邻的WO_4〜（2-）板的线上B轴方向。因此，相当不均匀的Bi-O距离和空置协调半球的形成应归因于铋的强烈需求，以形成更短的Bi-O键，以在其协调环境中使用其静电电荷。通过W位点的相关偏移和这些协作偏移的铋迁移和这些配方导致化合物中的铁电。通过诸如丙酮的分子侵入结构，容易实现这种繁殖。

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