title: Phase transitions and twinned low-temperature structures of tetraethylammonium tetrachloridoferrate(III).
abstract: The title compound, [(C2H5)4N][FeCl4], has at room temperature a disordered structure in the high-hexagonal space group P63mc. At 230 K, the structure is merohedrally twinned in the low-hexagonal space group P63. The volume has increased by a factor of 9 with respect to the room-temperature structure. At 170 and 110 K, the structure is identical in the orthorhombic space group Pca21 and twinned by reticular pseudomerohedry. The volume has doubled with respect to the room-temperature structure. All three space groups, viz. P63mc, P63 and Pca21, are polar and the direction of the polar axis is not affected by the twinning. In the P63 and Pca21 structures, all cations and anions are well ordered.
authors.affiliation: Bijvoet Center for Biomolecular Research, Crystal and Structural Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Martin
authors.initials: M
authors.lastname: Lutz
authors.affiliation: Debye Institute for Nanomaterials Science, Organic Chemistry and Catalysis, Faculty of Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands.
authors.forename: Yuxing
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Debye Institute for Nanomaterials Science, Organic Chemistry and Catalysis, Faculty of Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands.
authors.forename: Marc-Etienne
authors.initials: ME
authors.lastname: Moret
authors.affiliation: Debye Institute for Nanomaterials Science, Organic Chemistry and Catalysis, Faculty of Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands.
authors.forename: Robertus J M
authors.initials: RJ
authors.lastname: Klein Gebbink
keywords: crystal structure; group–subgroup relationship; low-temperature structures; phase transitions; tetraethylammonium tetrachloridoferrate(III); twinned structures