The synthesis and X-ray powder diffraction data for the long-known CaSiF6 and CaSiF6·2H2O species are reported. Their crystal structures have been determined from laboratory powder diffraction data by simulated annealing and full-profile Rietveld refinement methods. CaSiF6·2H2O was found to crystallize in the monoclinic P21/n space group with unit-cell parameters: a = 10.48107(9), b = 9.18272(7), c = 5.72973(5) Å, β = 98.9560(6)°, V = 544.733(8) Å3, and Z = 4. The crystal structure of CaSiF6·2H2O, eventually found to be isomorphous with SrSiF6·2H2O (but not with the Mg analogue—a hexahydrate phase), contains centrosymmetric [Ca(μ-H2O)2Ca]4+ dimers, interconnected by hexafluorosilicate anions, in a dense 3D framework. The crystal structure is completed by a further water molecule, terminally bound to the Ca2+ ion, which, consequently, attains a F5O3 octacoordination. Thermodiffractometric measurements allowed the determination of the linear and volumetric thermal expansion coefficients of CaSiF6·2H2O, which showed a minor contraction, along a, on heating. CaSiF6 is trigonal, space group R-3, a = 5.3497(3), c = 13.5831(11) Å, V = 336.66(5) Å3, and Z = 3, and isomorphous with several other species of MIIAIVF6 or MIAVF6 formulation, among which several silicates, germanates, and stannates.

中文翻译：

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粉末衍射法对无水和双水合六氟硅酸钙的结构表征

久负盛名的 CaSiF 的合成和 X 射线粉末衍射数据6和 CaSiF6·2H2报告了 O 物种。它们的晶体结构已通过模拟退火和全轮廓 Rietveld 细化方法从实验室粉末衍射数据中确定。碳化硅6·2H2发现 O 在单斜晶系中结晶磷21/n具有单胞参数的空间群：一种= 10.48107(9),b= 9.18272(7),C= 5.72973(5) 埃，β= 98.9560(6)°,五= 544.733(8) Å3， 和Z= 4. CaSiF的晶体结构6·2H2O，最终发现与 SrSiF 同晶6·2H2O（但不包括 Mg 类似物——六水合物相），含有中心对称的 [Ca(μ-H2○）2钙]4+二聚体，通过六氟硅酸阴离子相互连接，形成一个致密的 3D 框架。晶体结构由另一个水分子完成，末端与 Ca2+离子，因此，达到 F5○3八配位。热衍射测量允许确定 CaSiF 的线性和体积热膨胀系数6·2H2O，显示出轻微的收缩，沿着一种，加热时。碳化硅6是三角形的，空间群R-3,一种= 5.3497(3),C= 13.5831(11) 埃，五= 336.66(5) Å3， 和Z= 3，并且与其他几种米二一种四F6要么米一世一种五F6配方，其中几种硅酸盐、锗酸盐和锡酸盐。