Borate crystal chemistry in terms of the extended OD theory: topology and symmetry analysis

• Published in: Crystallography reviews 2005-07, Vol.11 (3), p.151-198
• Main Author: Belokoneva, Elena L.
• Format: Article
• Language: English
• Subjects: Extended order-disorder (OD) theory; Hexa-, penta-, tetra-, tri-, di-, polyborate crystal chemistry; Structure prediction and systematics
• ISSN: 0889-311X; 1476-3508
• DOI: 10.1080/08893110500230792

The crystal chemical analysis of the class of borates has been carried out using the extended Dornberger-Schiff order-disorder (OD) theory based on the recognition of building blocks of various dimensions. All of the borate structures are built from several fundamental building blocks typical for every group of hexa-, penta-, tetra-, tri-, diborates; polyborates contain combinations of these different units. Zero dimensional periodic blocks and the fundamental building blocks in the Christ, Clark, and Strunz systems are in fact the same. Every block possesses its own topology and local symmetry. Consecutive condensation of blocks to rods, layers and frameworks is governed by symmetry laws, that is together with the local symmetry of units the subject of OD-analysis. For all borate groups considered, symmetry groupoids of various ranks have been proposed for different condensation units. Structural-generic branches for borates have been distinguished, hypothetical structural variants predicted, and the positions of compounds in the Strunz system either confirmed or corrected. Successful application of symmetry-topological principles of extended OD-theory to the borates gives a tool for crystal chemical analysis of many other compound classes.