Bindi, L. & Evain, M. (2007) Gram-Charlier development of the atomic displacement factors into mineral structures: The case of samsonite, Ag4MnSb2S6. Am. Miner. 92 886–891.
Added by: Laurent Cournède (2016-03-10 22:02:30) |
Type de référence: Article DOI: 10.2138/am.2007.2364 Numéro d'identification (ISBN etc.): 0003-004X Clé BibTeX: Bindi2007b Voir tous les détails bibliographiques |
Catégories: MIOPS Mots-clés: atomic displacement parameters, crystal structure, crystal-structure determination, disordered crystals, pearceite, phase-transitions, polybasite, potentials, samsonite, silver distribution, temperature-dependence, x-ray, X-ray data Créateurs: Bindi, Evain Collection: Am. Miner. |
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Résumé |
During structure solution of Ag-, Cu-bearing minerals it is quite common to observe disorder. Ag+ and Cu+, indeed, can occur in different, but overlapping sites. The typical way to deal with these kind of minerals in structure determination is to use a split-atom model. This approach, however, has several disadvantages and may give rise to ambiguities. A solution to the problem can be the use of higher order tenser elements in the expression of the structure factors (the "non-harmonic approach"). This alternative approach gives, in cases of highly overlapping electron densities, an equivalent description of the split-atom model. The non-harmonic approach based upon a Gram-Charlier development of the atomic displacement factors can be useful in mineral sciences for the determination of still unknown structures. In addition, such an approach can be used to refine known structures with suspiciously high R values and/or high isotropic displacement parameters for the silver or copper atoms. As an example of the application of this method, we have reinvestigated the crystal structure of samsonite, Ag4MnSb2S6.
Added by: Laurent Cournède |