| Autor: |
Rastsvetaeva, R. K., Pekov, I. V., Nekrasov, Yu. V. |
| Předmět: |
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| Zdroj: |
Crystallography Reports; May2001, Vol. 46 Issue 3, p365, 3p |
| Abstrakt: |
The structure of a new representative of the labuntsovite family, which was found in the Khibiny alkaline massif (the Kola Peninsula), was established by the method of X-ray diffraction analysis. The unit-cell parameters are a = 14.365(7) Å, b = 13.887(7) Å, c = 7.814(2) Å, β = 117.36(5)°, sp. gr. Cm, R[sub aniso] = 0.058, 1385 F> 4σ(F). The mineral differs from other members of the family by the absence of Na-atoms and the high Ca-content. The Ca-polyhedron is reduced to a seven-vertex polyhedron (the average Ca-O distance is 2.48 Å) compared to the eight-vertex Na-polyhedron (the average Na-O distance is 2.57 Å). The structure channels are orderly occupied, thus lowering the symmetry to Cm. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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