Crystal structures of the RCuPbS 3 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds

Abstract

The crystal structures of the RCuPbS 3 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds (space group Cmcm, Pearson symbol oC28-4) were determined by means of X-ray single crystal diffraction ( a = 0.3925(1) nm, b = 1.2916(4) nm, c = 1.0161(3) nm, R1 = 0.0376 (HoCuPbS 3); a = 0.3916(1) nm, b = 1.2934(3) nm, c = 1.0106(2) nm, R1 = 0.0304 (ErCuPbS 3); a = 0.3911(1) nm, b = 1.2956(3) nm, c = 1.0064(3) nm, R1 = 0.0441 (YbCuPbS 3); a = 0.3899(1) nm, b = 1.2920(4) nm, c = 1.0030(3) nm, R1 = 0.0320 (LuCuPbS 3)) and X-ray powder diffraction ( a = 0.39413(3) nm, b = 1.2885(1) nm, c = 1.0262(1) nm, R Bragg = 0.0907 (TbCuPbS 3); a = 0.39297(3) nm, b = 1.2891(1) nm, c = 1.0205(1) nm, R Bragg = 0.0851 (DyCuPbS 3); a = 0.39096(3) nm, b = 1.29539(9) nm, c = 1.0078(1) nm, R Bragg = 0.0943 (TmCuPbS 3)). The structure of these compounds is related to the structure of KZrCuS 3 and can be described as a packing of R-centered octahedra, Cu-centered tetrahedra and Pb-centered trigonal prisms. The structures of the RCuPbS 3 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds are closely related to the structure of YCuPbS 3 (β-BaLaCuSe 3 structure type, space group Pnma) where S atoms form similar motifs and the positions of cations are identical.