The Lutetium-rich Indide Lu13Ni6In

The lutetium-rich indide Lu13Ni6In was synthesized from the elements by arc-melting and subsequent annealing in a sealed niobum container. At room temperature, the Lu13Ni6In structure is centrosymmetric, space group R3m, a = 919.74(10), c = 1828.9(2) pm, wR(2) = 0.0996, 666 F-2 values, 43 variables. It exhibits strong anisotropic displacement parameters U-33 for the Lu1 and U-22 for the Ni atoms. In going to low-temperature, Lu13Ni6In shows a phase transition (loss of the inversion symmetry) along with an ordering of Lu1. The structure was refined from 90 K single-crystal X-ray diffractometer data for an inversion twin: R3m, a = 918.97(4), c = 1820.27(7) pm, wR(2) = 0.0890, 1288 F-2 values, 56 variables. The low-temperature Lu13Ni6In structure can be described as a condensation of In@Lu-12 icosahedra, Ni2@Lu-6 trigonal prisms, and Ni@Lu-4 tetrahedra to layers that are stacked in ABC sequence. The driving force for superstructure formation is a strengthening of Lu-Ni bonding. Temperature dependent magnetic susceptibility measurements show Pauli paramagnetic behavior.