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Crystal chemistry of aeschynite-(Y) from the Western Alps; residual electron density on difference-Fourier map

Paola Bonazzi and Silvio Menchetti
Crystal chemistry of aeschynite-(Y) from the Western Alps; residual electron density on difference-Fourier map
European Journal of Mineralogy (December 1999) 11 (6): 1043-1049

Abstract

Crystal structure and chemical composition of five crystals of non-metamict aeschynite-(Y) from the Western Alps were investigated. In the whole the structure previously determined on heat-treated crystals of aeschynite was confirmed. Nevertheless an interesting feature emerged from the structure refinements concerning the presence of a residual density maximum of approximately 3/5 e (super -) /Aa (super 3) (C site) in the difference Fourier map. The addition of the C site to the structural model significantly improved the final R factors in all refined samples. The C site is asymmetrically located within an eight-fold cavity, similar in shape to that occupied by A cations. The short A-C distances led to the assumption that the presence of atoms in the C-site is coupled with structural vacancies in A. The implications in the calculation of chemical formulae are discussed.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 11
Serial Issue: 6
Title: Crystal chemistry of aeschynite-(Y) from the Western Alps; residual electron density on difference-Fourier map
Affiliation: Universita di Firenze, Dipartimento di Scienze della Terra, Florence, Italy
Pages: 1043-1049
Published: 199912
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 25
Accession Number: 2000-026837
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200009
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