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The crystal structure of rathite-I*

Published/Copyright: July 28, 2010
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Abstract

The crystal structure of rathite-I has been determined with the use of three-dimensional intensity data. Four chemical units of (Pb,Tl)3As4(As,Ag)S10 are contained in the unit-cell of the symmetry P21/a with a = 25.16 Å, b = 7.94 Å, c = 8.47 Å, β = 100°28′. The true symmetry of rathite-I may be triclinic. The solution was obtained from the similarity of the crystal structure to that of rathite-III and from a peculiar feature of the x-ray diagrams.

Among three independent Pb(Tl) atoms two are surrounded by nine S atoms and the other is surrounded by seven S atoms. As atoms have trigonal-pyramidal coordinations by S atoms. One As atom, however, is believed to occupy statistically two different trigonal-pyramidal S coordinations. Another As atom is partially replaced by Ag.

The structure is composed of two kinds of layers parallel to (100). Layers of the first kind have the composition (Pb,Tl)S3, and consist of coordination polyhedra around the Pb(Tl) atoms which are coordinated by nine S atoms. The layers of the second kind are composed of Pb(Tl), As(Ag) and S atoms, having a deformed PbS-type structure. Trigonal As-S3 pyramids are linked into strings of finite length.

Published Online: 2010-07-28
Published in Print: 1965-12
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