HYDROTHERMAL SYNTHESIS AND CRYSTAL-STRUCTURE DETERMINATION OF HEPTASILVER(I)-DISULFUR-TETRATHIOARSENATE(V), AG7S2(ASS4), WITH A SURVEY ON THIOARSENATE ANIONS

The compound Ag7S2(AsS4) has been synthesized by hydrothermal techniqu es and characterized by single-crystal X-ray diffraction data. Crystal s suitable for structure determination were grown from a mixture of el ementary silver, sulfur, and arsenic(III) sulfide in ammonia water. Th e compound is cubic, P2(1)3-T-4, with a = 10.475(1) Angstrom. The stru cture was solved by Patterson and Fourier methods and refined to R = 0 .044, R(w) = 0.028. The three crystallographically independent Ag atom s are surrounded by two, three, and four S atoms (Ag-S < 3.3 Angstrom) and three or four Ag atom neighbors (Ag-Ag < 3.3 Angstrom). These Ag polyhedra and the AsS4 tetrahedra form a three-dimensional framework. (C) 1994 Academic Press, Inc.