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On the Symmetry of the n=1 Ruddlesden‐Popper Phase Ca 2 FeO 3 Cl
Author(s) -
Kriworuschenko B.,
Kahlenberg V.
Publication year - 2002
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/1521-4079(200209)37:9<958::aid-crat958>3.0.co;2-f
Subject(s) - tetragonal crystal system , octahedron , crystallography , group (periodic table) , crystal structure , perovskite (structure) , type (biology) , symmetry (geometry) , phase (matter) , diffraction , chemistry , ion , perpendicular , materials science , physics , mathematics , geometry , optics , geology , paleontology , organic chemistry
Abstract Single crystals of Ca 2 FeO 3 Cl have been obtained as a by product during single crystal growth experiments of calcium ferrates from a CaCl 2 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). Ca 2 FeO 3 Cl belongs to the structure family of the Ruddlesden‐Popper series with n = 1, which is also referred to as the K 2 NiF 4 ‐type. Main building units are layers of perovskite type corner connected FeO 5 Cl‐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 Ca 2 FeO 3 Cl crystallizes in space group P 4. However, the present investigation shows clearly that this assignment is incorrect and that the compound has been described in an unnecessarily low symmetry.