Li₈Cu_12+<i>x</i>Al_6−<i>x</i>(<i>x</i>= 1.16): a new structure type related to Laves phases

Abstract

The new ternary lithium copper aluminide Li(8)Cu(12+x)Al(6-x) (x = 1.16) crystallizes in the P6(3)/mmc space group with six independent atom positions of site symmetries 3m. (Al/Cu mixture), 6m2 (Li atoms), 3m. (Al/Cu mixture and Li atoms) and .m. (Cu atoms). The compound is a derivative of the K(7)Cs(6) binary structure type and is related to the binary MgZn(2) Laves phase and the LiCuAl(2), MgCu(1.07)Al(0.93) and Mg(Cu(1-x)Al(x))(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.