Crystal structures of the R3CuGeSe7 (RÂ =Â Ce, Pr, Nd, Sm, Gd, Tb and Ho) compounds

The crystal structures of the R3CuGeSe7 compounds (R = Ce, Pr, Nd, Sm, Gd, Tb and Ho) (La3CuSiS7 structure type, space group P63, Pearson symbol hP24) were determined by means of X-ray single crystal diffraction (a = 1.0643(1) nm, c = 0.60973(7) nm, R1 = 0.0269 for Ce3CuGeSe7; a = 1.0559(1) nm, c = 0.6084(1) nm, R1 = 0.0301 for Pr3CuGeSe7; a = 1.0519(1) nm, c = 0.60707(9) nm, R1 = 0.0305 for Nd3CuGeSe7) and X-ray powder diffraction (a = 1.04216(3) nm, c = 0.60447(3) nm, RBragg = 0.0862 for Sm3CuGeSe7; a = 1.03491(8) nm, c = 0.60395(7) nm, RBragg = 0.0932 for Gd3CuGeSe7; a = 1.02940(5) nm, c = 0.60387(4) nm, RBragg = 0.0734 for Tb3CuGeSe7; a = 1.01978(7) nm, c = 0.60612(6) nm for Ho3CuGeSe7). The R atoms are surrounded by distorted trigonal prisms. A triangular surrounding exists for the Cu atoms. A tetrahedral surrounding exists for the Ge atoms.