Ordering of cations in the voids of the anionic framework of the crystal structure of catapleiite
- Russian Academy of Sciences, Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry (Russian Federation)
- Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)
- Moscow State University, Faculty of Geology (Russian Federation)
- Russian Academy of Sciences, Institute of the Problems of Chemical Physics (Russian Federation)
The pseudohexagonal crystal structure of the mineral catapleiite Na{sub 1.5}Ca{sub 0.2}[ZrSi{sub 3}(O,OH){sub 9}] {center_dot} 2(H{sub 2}O,F) from the Zhil'naya Valley in the central part of the Khibiny alkaline massif (Kola Peninsula, Russia) is studied by X-ray diffraction (XCalibur-S diffractometer, R = 0.0346): a = 20.100(4), b = 25.673(5), and c = 14.822(3) A; space group Fdd2, Z = 32, and {rho}{sub calcd} = 2.76 g/cm{sup 3}. Fluorine atoms substituting part of H{sub 2}O molecules in open channels of the crystal structure have been found for the first time in the catapleiite composition by microprobe analysis. The pattern of distribution of Na and Ca atoms over the voids of the mixed anionic framework consisting of Zr-octahedra and three-membered rings of Si-tetrahedra accounts for the pronounced pseudoperiodicity along the a and c axes of the pseudohexagonal unit cell and for the lowering of crystal symmetry to the orthorhombic one. It is shown that part of the hydrogen atoms of water molecules is statistically disordered; their distribution correlates with the pattern of the population of large eight-vertex polyhedra by Na and Ca atoms.
- OSTI ID:
- 22113626
- Journal Information:
- Crystallography Reports, Vol. 58, Issue 3; Other Information: Copyright (c) 2013 Pleiades Publishing, Ltd.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7745
- Country of Publication:
- United States
- Language:
- English
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