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The room temperature modification of Ag 8 SiS 6 is orthorhombic, space group Pna2 1 , with α = 15.024, b = 7.428, c = 10.533 Å, Z = 4. A complete single crystal X-ray structure analysis shows the structure to contain tetrahedral SiS 4 (4-) units (Si-S 2.094(12) ... 2.130(12) Å) besides isolated sulfide groups coordinated by Ag; the compound may thus be formulated as Ag 8 (SiS 4 )(S) 2 . The coordination of the Ag atoms by sulfur is distorted tetrahedral (Ag-S 2.557...2.757 A), approximately trigonal planar (Ag-S 2.386...2.775 A, with one additional weakly bonded axial S at 2.991 ... 3.330 Å), or linear (Ag-S 2.414... 2.443 Å). Within the (ordered) Ag sublattice the temperature factors are significantly higher than for Si and S, indicating a certain mobility of the Ag atoms. The arrangement of the thiosilicate -sulfide part of the structure is pseudocubic face-centered, showing the close structural relationship to the disordered cubic high temperature modification of Ag 8 GeTe 6 .
Krebs et al. (Fri,) studied this question.