Li20Mg6Cu13Al42: a new ordered quaternary superstructure to the icosahedral T-Mg32(Zn,Al)49 phase with fullerene-like Al60 cluster

Abstract

The new quaternary aluminide Li20Mg6Cu13Al42 was synthesized from the elements in a sealed tantalum crucible. The crystal structure was studied by single crystal and confirmed by X-ray powder diffraction. Li20Mg6Cu13Al42 {cI162, Im{\overline 3}, a = 13.8451 (2), R[F 2 > 2σ(F 2)] = 0.023} crystallizes as an ordered version of Mg32(Al,Zn)49 and Li—Cu—X (X = Al, Ga, Si) periodic crystals containing icosahedral clusters. The Li20Mg6Cu13Al42 structure can also be described as three-shell icosahedral clusters of [CuAl12@Li20Cu12@Al60], enclosed inside a distorted triacontahedron. The electronic structure calculations were performed by means of the TB-LMTO-ASA program and confirm the core–shell packing of these clusters. The isostructural compound of Li20Mg6Cu13Ga42 was found in a Li–Mg–Cu–Ga quaternary system.