Acta Crystallographica Section C

Crystal Structure Communications

Volume 64, Part 8 (August 2008)

inorganic compounds

 

Li₁₂Cu_16+xAl_26-x (x = 3.2): a new intermetallic structure type

V. Pavlyuk, G. Dmytriv, I. Tarasiuk, H. Pauly and H. Ehrenberg

Abstract: The new ternary lithium copper aluminide, Li₁₂Cu_16+xAl_26-x (x = 3.2), dodecalithium nonadecacopper tricosaaluminide, crystallizes in a new structure type with space group P4/mbm. Among nine independent atomic positions, two Al (one of which is statistically disordered with Cu) and three Li atoms have point symmetry m.2m, two statistically disordered Al/Cu atoms are in m.. sites, one Al atom is in a 4/m.. site and one Cu atom occupies a general site. The framework of Li₁₂Cu_16+xAl_26-x consists of pseudo-Frank-Kasper polyhedra enclosing channels of hexagonal prisms occupied by Li atoms. The crystallochemical peculiarity of this new structure type is discussed in relation to the derivatives from Laves phases (LiCuAl₂ and Li₈Cu_12+xAl_6-x) and to the well known CaCu₅ structure.

Formula: Li₁₂Cu_19.21Al_22.84

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