CRYSTALLOGRAPHIC ANALYSIS OF STRUCTURES ASSOCIATED WITH A NUMBER OF Tl- AND Ag-CONTAINING SULFIDES: the COMPOSITION-SYMMETRY CORRELATION
S. V. Borisov, S. A. Magarill, N. V. Pervukhina
Keywords: кристаллографический анализ, катионные и анионные подрешетки, сульфиды с Tl и Ag, стехиометрия катион/анион, crystallographic analysis, cation and anion sublattices, sulfides with Tl and Ag, cation/anion stoichiometry
Abstract
A crystallographic analysis is conducted of the structures of orthorhombic mineral sicherite TlAg2(As,Sb)3S6, monoclinic synthetic sulfide Tl3Ag3Sb2S6 , and triclinic mineral raberite Tl5Ag4As6SbS15. In the first two structures, the large and heavy Tl+ cation forms, together with the other cations, ordered “skeletal” frameworks with F and I cation sublattices that are close to cubic ones. In the structure of raberite, the Tl and Ag cations undergo, together with the sulfur anions, two-dimensional ordering by a zone of closely packed crystallographic planes, which generate a pseudohexagonal symmetry. The deviations from the 1 cation/anion stoichiometry are compensated: in the second structure, by a local consolidation of cations (to a distance Tl-Ag = 2.96 Å) and, in the third structure, through the formation of a dumbbell pair As-Ag (2.68 Å), which occupies one position in the sublattice.
|
