Crystal Structures of NbOI3 and NbOBr3 – Polar Double Chains in Different Non‐centrosymmetric Structures |
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Authors: | Sabina Hartwig Harald Hillebrecht Prof Dr |
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Institution: | 1. Freiburg, Albert‐Ludwigs‐Universit?t Freiburg, Institut für Anorganische und Analytische Chemie;2. Freiburger Materialforschungszentrum FMF, Stefan‐Maier‐Str. 25, D‐79104 Freiburg, Germany |
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Abstract: | NbOI3 was obtained from a reaction of Nb2O5, Nb, and I2. Single crystals free from disorder were a by‐product from a reaction with additional CsI. The monoclinic crystal structure (C2, a = 14.624(3) Å, b = 3.9905(8) Å, c = 12.602(3) Å, β = 120.4(3)°, Z = 4, R1(F) = 0.0368, wR2(F2) = 0.0804) represents a new structure type which is built up by distorted octahedral NbI4O2 with unequal O‐atoms in trans‐position. The octahedra are linked to dimers by a common edge of iodine atoms and to double chains by the apical oxygen atoms. A non‐centrosymmetric structure results because the short Nb–O distances point to the same direction and the polar double chains are parallel. The crystal structure of NbOBr3 (NbOCl3‐type, , a = 11.635(6) Å, c = 3.953(2) Å, R1(F) = 0.082, wR2(F2) = 0.174) shows the same polar double chains but the dimeric units Nb2Br6O2 are orthogonal. |
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Keywords: | Niobium Niobium oxide halide Polar structures Crystal structure Double chain structure |
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