Redetermination of kovdorskite, Mg2PO4(OH)·3H2O

• Published in: Acta Crystallographica Section E Structure Reports Online
• Main Authors: Morrison, Shaunna M., Downs, Robert T., Yang, Hexiong
• Format: Text
• Language: English
• Published: International Union of Crystallography 2012
• Subjects: Inorganic Papers; Kola Peninsula; Kovdor; kola peninsula
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3274836; http://www.ncbi.nlm.nih.gov/pubmed/22346789; https://doi.org/10.1107/S1600536812000256

The crystal structure of kovdorskite, ideally Mg2PO4(OH)·3H2O (dimagnesium phosphate hydroxide trihydrate), was reported previously with isotropic displacement paramaters only and without H-atom positions [Ovchinnikov et al. (1980 ▶). Dokl. Akad. Nauk SSSR. 255, 351–354]. In this study, the kovdorskite structure is redetermined based on single-crystal X-ray diffraction data from a sample from the type locality, the Kovdor massif, Kola Peninsula, Russia, with anisotropic displacement parameters for all non-H atoms, with all H-atom located and with higher precision. Moreover, inconsistencies of the previously published structural data with respect to reported and calculated X-ray powder patterns are also discussed. The structure of kovdorskite contains a set of four edge-sharing MgO6 octa­hedra inter­connected by PO4 tetra­hedra and O—H⋯O hydrogen bonds, forming columns and channels parallel to [001]. The hydrogen-bonding system in kovdorskite is formed through the water mol­ecules, with the OH− ions contributing little, if any, to the system, as indicated by the long H⋯A distances (>2.50 Å) to the nearest O atoms. The hydrogen-bond lengths determined from the structure refinement agree well with Raman spectroscopic data.