Preparation and Crystal Structure of the Isotypic Carbides Ln3.67TC6 (Ln = rare earth elements; T = Mn, Fe, Ru) and Eu3,16NiC6

Abstract

Abstract The 14 carbides Ln3.67MnC6 (Ln = La-Nd) and Ln3.67TC6 (Ln = La-Nd, Sm; T = Fe, Ru) were prepared from the elemental components by arc-melting and subsequent annealing. Eu3.16NiC6 was obtained from a lithium flux. The crystal structures of these nearly isotypic, hexagonal compounds (P63/m, Z = 2) were determined from single-crystal X-ray data; La3.67- FeC6: a = 878.7(2), c = 535.1(1) pm, R = 0.052 for 548 structure factors and 25 variable parameters; Eu3.16NiC6: a -860.0(1), c = 548.2(2) pm, R = 0.015 for 606 structure factors and 25 variables. The structures differ from the previously reported Gd3Mn2C6 structure by the occupancy of one manganese position by rare earth atoms. Since the lanthanum atoms are larger than the manganese atoms, only two thirds of these manganese positions can be occupied by the lanthanum atoms in La3.67FeC6. Eu3.16NiC6 has similar atomic positions. The C-C bond distances in the C2 pairs are 130(2) and 126.5(5) pm in the La and Eu compounds, respectively. Magnetic susceptibility measurements with a SQUID magnetometer indicate La3.67FeC6 to be Pauli paramagnetic. A test for superconductivity was negative down to 3 K.