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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Investigation of the CsxRb1-xTiOAsO4 series. I. Crystal structure analysis and pseudosymmetry
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Investigation of the CsxRb1-xTiOAsO4 series. I. Crystal structure analysis and pseudosymmetry

机译：CsxRb1-xTiOAsO4系列的研究。一，晶体结构分析与拟对称

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摘要

Refinements of five crystals in the Cs2xRb2-2x-Ti2O2As2O8 series, caesium rubidium titanyl arsenate, with x = 0.07, 0.31, 0.58, 0.71 and 0.86, which are compositional analogues of KTiOPO4 (KTP), have been completed at 293 K and two (x = 0.71, 0.86) at low temperature. All the structures are found to be orthorhombic (space group Pna2(1)) and are isostructural with KTP, although there is evidence of some Cs disorder over additional sites in the framework, particularly at the Cs-rich end of the series, as discussed in Part II [Thomas & Womersley (1998). Acta Cryst. B54, 645-651]. Unusually large U-33 parameters for shared Cs/Rb sites are observed and are shown to be the result of the existence of separate sites for Ca and Rb within the structural framework, although the coordinates of these sites cannot be resolved convincingly. The structural changes in the TiO6/AsO4 framework. required to accommodate an increasing fraction of the larger Cs cation across the series and under cooling to 120 K are elucidated. Finally, the deviations of the room-temperature and low-temperature structures from the high-temperature prototypic structure (space group Pnan) are examined and suggest that the phase-transition temperature should increase linearly from CsTiOAsO4 to RbTiOAsO4. [References: 29]
机译：Cs2xRb2-2x-Ti2O2As2O8系列中的五个晶体精制砷酸铯rub钛酸铯（x = 0.07、0.31、0.58、0.71和0.86）是KTiOPO4（KTP）的组成类似物，已在293 K上完成精制，而两个（ x = 0.71，0.86）在低温下。已发现所有结构都是正交的（空间群Pna2（1）），并且与KTP是同构的，尽管有证据表明框架中其他位点（特别是在系列中富含Cs的末端）上存在一些Cs异常。在第二部分[Thomas＆Womersley（1998）。 Acta Cryst。 B54，645-651]。观察到共享的Cs / Rb位置异常大的U-33参数，并显示这是结构框架内存在Ca和Rb单独位置的结果，尽管这些位置的坐标无法令人信服地解析。 TiO6 / AsO4骨架的结构变化。阐明了在整个系列中容纳越来越大的Cs阳离子所需的一部分，并需要冷却至120K。最后，研究了室温和低温结构与高温原型结构（空间群Pnan）之间的偏差，表明相变温度应从CsTiOAsO4到RbTiOAsO4线性增加。 [参考：29]

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