The crystal structure of the R6Si4S17 (R = Pr, Nd and Sm) compounds

The crystal structure of the R6Si4S17 compounds (R = Pr, Nd and Sm) (Ce6Si4S17 structure type, space group P1¯, Pearson symbol aP54) was determined by means of X-ray single crystal diffraction (a = 0.8902(1) nm, b = 0.9934(1) nm, c = 1.4206(2) nm, α = 82.19(1)°, β = 86.94(1)°, γ = 89.40(1)°, R1 = 0.0389 for Pr6Si4S17; a = 0.8880(1) nm, b = 0.9903(1) nm, c = 1.4168(2) nm, α = 82.11(1)°, β = 87.04(1)°, γ = 89.31(1)°, R1 = 0.0226 for Nd6Si4S17; a = 0.88300(8) nm, b = 0.9779(1) nm, c = 1.4047(1) nm, α = 82.126(8)°, β = 87.338(7)°, γ = 89.018(8)°, R1 = 0.0224 for Sm6Si4S17). The Pr atoms are surrounded by distorted trigonal prisms with two (three) additional atoms or octahedra with one additional atom. Tetrahedral surrounding exists for all Si atoms. The S atoms are surrounded by three (triangles) or four (tetrahedra) atoms.