Refinement of the mangan-neptunite crystal structure
- 50 Downloads
The crystal structure of mangan-neptunite, a manganese analogue of neptunite, has been refined in two space groups (Cc and C2/c). The mineral is monoclinic, with the correct space group Cc; the unit-cell dimensions are: a = 16.4821(6), b = 12.5195(4), c = 10.0292(3) Å, β = 115.474(1)°, and V = 1868.31 Å3. The crystal structure has been refined to R 1 = 0.0307 (wR 2 = 0.0901) on the basis of 4892 observed reflections with |F hkl | ≥ 4σ|F hkl |. The most plausible acentric model is caused by the Ti- and (Fe, Mn, Mg)-ordering in the structure. Ti-octahedrons are strongly distorted and consist of short bond Ti-O (1.7 Å), one long bond (2.2 Å), and four equal bonds (2.0 Å). Fe-octahedrons are regularly shaped, with all Fe-O bonds being approximately identical.
KeywordsBarium Titanate Short Bond Alkaline Pluton Tetragonal BaTiO Octahedral Distortion
Unable to display preview. Download preview PDF.
- 1.S. V. Borisov, R. F. Klevtsov, V. V. Bakakin, and N. V. Belov, “Crystal Structure of Neptunite,” Kristallografiya 10(6), 815–821 (1965).Google Scholar
- 3.J. Harada, T. Pedersen, and Z. Barnea, “X-Ray and Neutron Diffraction Study of Tetragonal Barium Titanate,” Acta Crystallogr. A26, 336–344 (1970).Google Scholar
- 5.E. P. Meagher and G. A. Lager, “Polyhedral Thermal Expansion in the TiO2 Polymorphs: Refinement of the Crystal Structures of Rutile and Brookite at High Temperature,” Can. Mineral. 17, 77–85 (1979).Google Scholar
- 7.A. J. Speer and G. V. Gibbs, “The Crystal Structure of Synthetic Titanite, CaTiOSiO4, and Domain Textures of Nature Titanites,” Am. Mineral. 61, 238–247 (1976).Google Scholar
- 8.V. N. Yakovenchuk, G. Yu. Ivanyuk, Ya. A. Pakhomovsky, and Yu. P. Men’shikov, Khibiny (Laplandia Minerals, 2005).Google Scholar