Single crystals of Ca2FeO3Cl have been obtained as a by product during single crystal growth experiments of calcium ferrates from a CaCl2 flux. The reddish‐brown optically uni‐axial crystals adopt the tetragonal space group P4/nmm with a = 3.8381(4) Å and c = 13.685(2) Å and Z = 2 formula units per cell. The structure has been determined from a single crystal diffraction data set collected at room conditions and refined to final residual R(|F|) = 0.053 for 163 observed independent reflections with I > 2σ(I). Ca2FeO3Cl belongs to the structure family of the Ruddlesden‐Popper series with n = 1, which is also referred to as the K2NiF4‐type. Main building units are layers of perovskite type corner connected FeO5Cl‐octahedra perpendicular to [001]. The two crystallographically independent calcium ions are located between the octahedral layers and are coordinated by nine ligands each: Ca1 (4×O + 5×Cl) and Ca2 (9×O). Following prior studies Ca2FeO3Cl crystallizes in space group P4. However, the present investigation shows clearly that this assignment is incorrect and that the compound has been described in an unnecessarily low symmetry.

structure structure (solids and liquids) D 2000 -006On the Symmetry of the n=1 Ruddlesden-Popper Phase Ca 2 FeO 3 Cl.-Reddish-brown optically uni-axial single crystals of the title compound are obtained from CaCO 3 and Fe 2 O 3 in a CaCl 2 flux (1050 • C, 6 h). Ca 2 FeO 3 Cl crystallizes in the tetragonal space group P4/nmm with Z = 2 (single crystal XRD). The main building units of the structure are layers of perovskite type corner-connected FeO 5 Cl octahedra. The two crystallographically independent Ca ions are located between the octahedral layers and are coordinated by nine ligands each. -(KRIWORUSCHENKO, B.; KAHLENBERG, V.; Cryst. Res. Technol. 37 (2002) 9, 958-963; Fachber. Geowiss., Univ. Bremen, D-28359 Bremen, Germany; EN)