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GEOREF RECORD

Crystal structure of Pb (sub 6) [Ge (sub 6) O (sub 18) ].2H (sub 2) O, a lead cyclo-germanate similar to the mineral dioptase

Hans Hermann Otto and Hans-Jurgen Brandt
Crystal structure of Pb (sub 6) [Ge (sub 6) O (sub 18) ].2H (sub 2) O, a lead cyclo-germanate similar to the mineral dioptase
European Journal of Mineralogy (April 1996) 8 (2): 301-310

Abstract

Pb (sub 6) [Ge (sub 6) O (sub 18) ]2H (sub 2) O crystallizes as transparent colourless trigonal needles, with space group R<$E 3 back 40 up 40 ->, a 15.6476, c 7.3119 Aa; Z = 3; D 6.44 g/cm (super 3) . Powder XRD data after least-squares refinement to R 0.033 shows the structure to consist of sandwiched hetero-polyhedral rings with straight channels down [001]. Isolated and partly expanded rings of six corner-sharing GeO (sub 4) tetrahedra are bonded together vertically by crown-shaped Sechser rings of flat PbO (sub 5+1) pyramids with shared corners, which themselves share edges laterally. Lone electron pairs of lead, which complete the pyramids in a Psi -octahedral arrangement, point towards the channel centres. The channels have a free diameter of approximately 2.5 Aa and confine well-ordered pairs of water molecules which can be degassed by heating. A crystal-chemical and morphological comparison is drawn with dioptase, Cu (sub 6) [Si (sub 6) O (sub 18) ]6H (sub 2) O. This lead cyclo-germanate is the first compound found to have pure [Ge (sub 6) O (sub 18) ] (super 12-) single rings.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 8
Serial Issue: 2
Title: Crystal structure of Pb (sub 6) [Ge (sub 6) O (sub 18) ].2H (sub 2) O, a lead cyclo-germanate similar to the mineral dioptase
Affiliation: TU Clausthal, Materialwissenschaftliche Kristallographie, Clausthal-Zellerfeld, Federal Republic of Germany
Pages: 301-310
Published: 199604
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 29
Accession Number: 1996-044102
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199615
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