Startseite The crystal structure of freieslebenite, PbAgSbS3*
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The crystal structure of freieslebenite, PbAgSbS3*

Veröffentlicht/Copyright: 28. Juli 2010
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Abstract

The crystal structure of freieslebenite, PbAgSbS3, has been determined with three-dimensional counter data (R = 3.2%). The structure was solved by the method of key shifts. The obtained structure is different from the model proposed by Hellner (1957); instead, it is isomorphous with marrite, PbAgAsS3, an As analogue of freieslebenite. The crystal is monoclinic, space group P21/a, with a = 7.518(1), b = 12.809(4), c = 5.940(1) Å, β = 92.25(1)° and Z = 4.

The structure is a superstructure of a PbS-type substructure. The displacements of the atoms from the ideal substructure are less in freieslebenite than in marrite, probably because of the larger atomic radius of Sb than that of As. Sb has the usual trigonal-pyramidal coordination of S atoms. The Sb–S distances are 2.431, 2.453 and 2.480(4) Å. The SbS3 pyramids are isolated from each other. Pb is coordinated with six S atoms in a distorted octahedral arrangement. The Pb–S distances range from 2.806 to 3.167(4) Å. Ag has three nearest S neighbours at the distances 2.522, 2.575 and 2.687(4) Å. The AgS3 group is nearly planar. A fourth S atom is at a distance of 2.928(4) Å from Ag, the Ag–S being approximately perpendicular to the AgS3 plane. The temperature factor of Ag is significantly larger and more anisotropic than those of the other atoms; this feature is common among related structures.

Published Online: 2010-07-28
Published in Print: 1974-04
Heruntergeladen am 27.10.2025 von https://www.degruyterbrill.com/document/doi/10.1524/zkri.1974.139.1-2.85/html?lang=de
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