Low- and high-temperature crystal structures of Ti।₃

Titelangaben

Angelkort, Joachim ; Schönleber, Andreas ; van Smaalen, Sander:
Low- and high-temperature crystal structures of Ti।₃.
In: Journal of Solid State Chemistry. Bd. 182 (2009) Heft 3 . - S. 525-531.
ISSN 0022-4596
DOI: https://doi.org/10.1016/j.jssc.2008.11.028

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Abstract

Temperature-dependent, single-crystal X-ray diffraction of Ti।₃ has indicated that this compound undergoes a first-order phase transition at T c = 323 ± 2 K . Accurate structural parameters are reported for the high-temperature crystal structure at T = 326 K (hexagonal cell, a = 7.1416 (5)Å , c = 6.5102 (4)Å , Z = 2 , space group P6₃/mcm) and for the low-temperature structures at both 273 and 100 K (orthorhombic symmetry, space group Pmnm , Z = 4 , lattice parameters at 273 K: a = 12.3609 (7)Å, b = 7.1365 (5)Å , c = 6.5083 (4)Å and at 100 K: a = 12.2728 (7)Å , b = 7.0857 (5)Å , c = 6.4817 (4)Å ). Above T c , Ti।₃ possesses the Ti।₃ structure type containing chains of equidistant metal atoms. A twofold superstructure develops below T c , resulting in the RuBr₃ structure type that is characterized by a dimerization of the metal chains. The magnitude of the distortion is found to be the largest amongst the known transition metal trihalides. It thus provides an explanation for the inclination of Ti।₃ towards the RuBr₃ structure type, despite the fact that metal–metal bonds are weaker in iodides than in chlorides or bromides.