Orthorhombic aluminium oxyfluoride, AlOF

• Published in: Acta crystallographica. Section C, Crystal structure communications Vol. 65; no. 4; pp. i20 - i22
• Main Authors: Vasiliev, Alexander D., Melnikova, Svetlana V., Isaenko, Lyudmila I.
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England International Union of Crystallography 01-04-2009; Wiley Subscription Services, Inc
• Subjects: Atoms & subatomic particles; Chemical bonds; Chemical compounds; Crystal structure; Crystallography
• ISSN: 0108-2701; 1600-5759
• DOI: 10.1107/S0108270109010671

Crystals of the title compound were extracted from the bulk of grown SrAlF5 crystals as unexpected inclusions that were identified as the long sought after aluminium oxyfluoride. The structure of AlOF is built up from tetrahedral and octahedral polyhedra. Each tetrahedron is bisected by a mirror plane, with the Al atom and two vertex anions in the plane. All tetrahedral vertices are positions of competing oxide and fluoride ions and are shared with octahedra. These shared vertices belong to two octahedral edges which join the octahedra to form infinite zigzag chains. The chains are strung along twofold screw axes that run parallel to the unit‐cell b axis. The remaining two octahedral vertices are occupied only by fluoride ions. A small deficiency in the occupation of the octahedral Al position was suggested by the refinement. However, the stoichiometry of the compound is AlOF within experimental uncertainty. The Al—F(O) distances are separated into three groups with average values of 1.652 (3) (tetrahedra), 1.800 (2) (octahedra) and 1.894 (2) Å (octahedra). This structure differs widely from the reported tetragonal phase Al1−xO1−3xF1+3x (x = 0.0886) [Kutoglu (1992). Z. Kristallogr.199, 197–201], which consists solely of octahedral structural units.