Structure and ferroelasticity of tetramethylammonium-hexafluoroosmate(IV), (TMA)2[OsF6]

Küppers, H.; Göbel, O.; Bruhn, C. and Schmahl, Wolfgang W. (2001): Structure and ferroelasticity of tetramethylammonium-hexafluoroosmate(IV), (TMA)2[OsF6]. In: Zeitschrift fur Kristallographie, Vol. 216, No. 6: pp. 354-360

Abstract

(TMA)2[OsF6] has at room temperature a rhombohedral structure (space group R3̄) which is pseudo-cubic (K2[PtCl6]-type). a=8.0565(6) Å, c = 20.020(3) Å (hexagonal setting). Double refraction decreases linearly with increasing temperature and disappears above 434 K which indicates cubic symmetry of the high temperature phase. The change from the cubic high temperature structure to the rhombohedral structure is characterized by a ferrorotative tilt of the [OsF6] octahedra and the TMA tetrahedra. Evidence of ferroelasticity follows from the switching of the trigonal c-axis by the application of directional pressure. The phase transitions of (TMA)2[OsF6] (Fm3̄m → R3̄) and of the recently reported (TMA)2[PtF6] and (TMA)2[IrF6] (Fm3̄m → I4/m) are described by Landau’s theory.

• Item Type: Journal article
• Faculties: Geosciences > Department of Earth and Environmental Sciences > Crystallography and Materials Science
• Subjects: 500 Science > 550 Earth sciences and geology
• Language: English