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  • 1
    ISSN: 0044-2313
    Keywords: Sodium iron fluoride ; weberite structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Struktur von Na2Fe2F7 und Strukturbeziehungen in der Weberitfamilie Na2MIIMIIIF7Die gemischtvalente Verbindung Na2Fe2F7 kristallisiert im monoklinen Weberit-Typ von Na2CuFeF7-II (M-II), Raumgruppe C2/c, Z = 16, a = 12,676, b = 7,422, c = 24,710 Å, β = 99,97°. Die Verfeinerung mit F2-Daten ergab wR(F2) = 0,117 für alle 2 645 Reflexe, R = 0,057 für 1 258 Reflexe mit Fo 〉 4σ(F). Auf der Grundlage dieser und anderer neuer Einkristalluntersuchungen werden die Strukturen der Weberite Na2MIIMIIIF7 in vier Haupttypen eingeteilt: O-I ist der „klassische“ orthorhombische Weberit (RG Imma), wie er im Mineral Na2MgAlF7 auftritt, und von dem sich zwei niedriger symmetrische Varianten, O-II (Na2CuCrF7-Typ) und O-III (Na2NiInF7), ableiten. Der zweite M-I und dritte M-II Typ sind monoklin (z. B. Na2CuFeF7-I and -II), der vierte Typ T ist trigonal (Na2MnFeF7). Die strukturellen Verwandtschaften innerhalb der Weberitfamilie werden diskutiert und die Zusammenhänge aufgezeigt, die es erlauben, diese Weberite ebenso wie die Pyrochlore als Subtraktionsabkömmlinge des Fluorittyps zu betrachten.
    Notes: The mixed valence compound Na2Fe2F7 crystallizes in the monoclinic weberite structure of the Na2CuFeF7-II type (M-II), space group C2/c, Z = 16, a = 12.676, b = 7.422, c = 24.710 Å, β = 99.97°. Refinement on F2 led to wR(F2) = 0.117 for all 2 645 reflections, R = 0.057 for 1 258 refl. with Fo 〉 4σ(F). On the basis of this and other recent single crystal investigations the structures of weberites Na2MIIMIIIF7 are classified in four main structure types: O-I is the ‘classical’ orthorhombic weberite type (S.G. Imma) encountered e.g. in the mineral Na2MgAlF7, from which two lower symmetric variants O-II (Na2CuCrF7 type) and O-III (Na2NiInF7) are deriving. The second M-I and third M-II basic type are monoclinic (e. g. Na2CuFeF7-I and -II), the fourth type T is trigonal (Na2MnFeF7). The structural relations within the weberite family are discussed and the connections established, which allow to regard these weberites as well as the pyrochlores as subtraction derivatives of the fluorite type.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 1692-1697 
    ISSN: 0044-2313
    Keywords: Sodium copper scandium fluoride ; sodium zinc aluminium fluoride ; weberite structure ; crystal structure determination ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Crystal Structures of the Weberites Na2CuScF7 and Na2ZnAlF7At single crystals of the orthorhombic weberites Na2CuScF7 (Pmnb, Z = 4) and Na2ZnAlF7 (Imma, Z = 4) X-ray structure determinations were performed. Na2CuScF7 (Na2ZnAlF7): a = 726.0 (709.2), b = 1053.4 (1009.2), c = 765.8 (733.7) pm; R1 = 0.030 (0.042) for 887 (363) observed and independent reflections. The resulting average distances of the octahedrally coordinated metal atoms are: Cu—F = 200.7 pm, Sc—F = 201.7 pm; Zn—F = 198.8 pm, Al—F = 180.1 pm. Some structural relations and the variation in the bridge angles of the corner-sharing octahedra are discussed.
    Notes: An Einkristallen der orthorhombischen Weberite Na2CuScF7 (Pmnb, Z = 4) und Na2ZnAlF7 (Imma, Z = 4) wurden röntgenographische Strukturbestimmungen durchgeführt. Na2CuScF7 (Na2ZnAlF7): a = 726,0 (709,2), b = 1053,4 (1009,2), c = 765,8 (733,7) pm; R1 = 0,030 (0,042) für 887 (363) beobachtete und unabhängige Reflexe. Die resultierenden mittleren Abstände für die oktaedrisch koordinierten Metallatome sind: Cu—F = 200,7 pm, Sc—F = 201,7 pm; Zn—F = 198,8 pm, Al—F = 180,1 pm. Die Stukturverhältnisse und die Unterschiede in den Brückenwinkeln der eckenverknüpften Oktaeder werden diskutiert.
    Additional Material: 1 Ill.
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