Crystal structure of the R6Pb2Se11 (RÂ =Â Y, Dy and Ho) compounds

The crystal structures of the R6Pb2Se11 (R = Y, Dy and Ho) compounds (space group Cmcm, Pearson symbol oC76) were determined by means of X-ray single crystal diffraction: a = 0.40620(8) nm, b = 1.3467(2) nm, c = 3.7624(7) nm, R1 = 0.0593 (Y6Pb2Se11) and X-ray powder diffraction: a = 0.40772(8) nm, b = 1.3458(3) nm, c = 3.7589(9) nm (Dy6Pb2Se11); a = 0.40561(2) nm, b = 1.34018(6) nm, c = 3.7525(1) nm, RI = 0.0722 (Ho6Pb2Se11). The crystal structure of the R6Pb2Se11 (R = Y, Dy and Ho) compounds can be described as a packing of columns of R-centered octahedra, M (0.50Y + 0.50Pb)- and Pb-centered trigonal prisms with one and two additional atoms, respectively.