Pyroelectric Na(H3O) [I(OH)3O3]: Room temperature crystal structure

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Abstract
Na(H3O)[I(OH)3O3] is pyroelectric at room temperature and crystallizes in the space group R3 with lattice constants at 298 °K of a=6.04272(6) and c=13.23165(2) Å for CuKα1 =1.54062 Å. There are three formulas in the unit cell. The integrated intensities of 2081 structure factors, within two‐thirds of a sphere of reflection with (sinϑ) λ?1.2 Å−1, were measured on a CAD‐4 diffractometer with Nb‐filtered MoKα radiation. The crystal structure was solved by Patterson and Fourier series methods and refined by the method of least squares with 1102 symmetry‐independent Fmeas. The final agreement index R =0.015 for a model in which all atoms undergo anisotropic thermal vibration except for the hydrogens, which were refined with isotropic temperature factors. The I(OH)3O3−2 ion is octahedral, with I–O distance of 1.844(2) Å and I–OH distance of 1.920(2) Å. Strong hydrogen bonds of 2.544(1) Å connect oxonium and I(OH)3O3−2 ions in sheets normal to the polar axis. Weaker intersheet hydrogen bonds of 2.697(2) Å connect the OH− surfaces of one sheet to the O− surfaces of adjacent sheets.