Study of the bipyramidal site in magnetoplumbite-like compounds, SrM12O19 (M = Al, Fe, Ga)
| Autor: | M. Ohgaki, Fumiyuki Marumo, Kiyoaki Tanaka, K. Kimura, Hideki Morikawa |
|---|---|
| Rok vydání: | 1990 |
| Předmět: |
chemistry.chemical_classification
Diffraction Chemistry Stereochemistry Anharmonicity Crystal structure Condensed Matter Physics Electronic Optical and Magnetic Materials Inorganic Chemistry Trigonal bipyramidal molecular geometry Crystallography Bipyramid Group (periodic table) Atom Materials Chemistry Ceramics and Composites Physical and Theoretical Chemistry Inorganic compound |
| Zdroj: | Journal of Solid State Chemistry. 87:186-194 |
| ISSN: | 0022-4596 |
| DOI: | 10.1016/0022-4596(90)90081-8 |
| Popis: | Structures of magnetoplumbite-type crystals Sr M 12 O 19 ( M = Al, Fe, Ga) have been refined by the single-crystal X-ray diffraction method. The space group is P 6 3 / mmc with Z = 2. The cell dimensions are a = 5.5666(2) and c = 22.0018(8) A for SrAl 12 O 19 , a = 5.8836(1) and c = 23.0376(9)A for SrFe 12 O 19 , and a = 5.7929(1) and c = 22.8123(7) A for SrGa 12 O 19 at 22°C. Four structural models were tested with respect to the states of M atoms at trigonal bipyramidal sites: central atom and split atom models with and without anharmonic thermal vibrations. The simple split atom model gave lower R w values than the central atom model with anharmonic thermal vibrations for SrAl 12 O 19 and SrGa 12 O 19 , whereas it gave an R w value approximately equal to that given by the central atom model with anharmonic vibration for SrFe 12 O 19 . The present study suggested that the potential around the M atom with trigonal bipyramidal coordination has double minima in all the magnetoplumbite-type crystals at lower temperatures. |
| Databáze: | OpenAIRE |
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