The Ag2S–In2S3–Si(Ge)S2 systems and crystal structure of quaternary sulfides Ag2In2Si(Ge)S6

Isothermal sections of quasi-ternary systems Ag2S–In2S3–Si(Ge)S2 at 298 K were constructed using XRD results. Vertical sections Ag2S–In2S3, AgInS2–SiS2, AgIn5S8–Ag1.57SiS2.79 were investigated in the Ag2S–In2S3–SiS2 system. Two new quaternary compounds were discovered in the systems, Ag2In2SiS6 (melts incongruently at 1133 K) and Ag2In2GeS6. Both compounds crystallize in the monoclinic structure (structural type Ag2In2GeSe6, space group Cc) with lattice parameters a = 1.21379(3) nm, b = 0.71681(2) nm, c = 1.21171(4) nm, β = 109.252(2)° and a = 1.22089(4) nm, b = 0.72115(3) nm, c = 1.21978(5) nm, β = 109.508(2)°, respectively. Atomic parameters were refined in the isotropic approximation to RI = 0.0746, RP = 0.1256 (Ag2In2SiS6); RI = 0.0657, RP = 0.1189 (Ag2In2GeS6).