Li8Cu12+xAl6-x (x = 1.16): a new structure type related to Laves phases

The new ternary lithium copper aluminide Li8Cu12+xAl6−x (x = 1.16) crystallizes in the P63/mmc space group with six independent atom positions of site symmetries \overline{3}m. (Al/Cu mixture), \overline{6}m2 (Li atoms), 3m. (Al/Cu mixture and Li atoms) and .m. (Cu atoms). The compound is a derivative of the K7Cs6 binary structure type and is related to the binary MgZn2 Laves phase and the LiCuAl2, MgCu1.07Al0.93 and Mg(Cu1−xAlx)2 (x = 0.465) ternary Laves phases. The coordination polyhedra of the atoms in this structure are icosa­hedra (Cu atoms), slightly distorted icosa­hedra and bicapped hexa­gonal anti­prisms (Al/Cu statistical mixture), and Frank–Kasper and distorted Frank–Kasper polyhedra (Li atoms). All inter­atomic distances indicate metallic type bonding.