The title compounds Zn13(CrxAl1–x)27 (x = 0.34–0.37) were obtained by melting the pure elements at 923 K, and followed by a heat treatment at 723 K in a tantalum container. According to single crystal structural analysis, the title compounds crystallize in the rhombohedral system, adopting a new structure type (R-3m, a = 7.5971(8), c = 36.816(6), for crystal I). Single crystal X-ray structural analysis reveals a statistical mixing of Cr/Al in their crystallographic positions. Single crystal and powder X-ray diffraction as well as energy dispersive X-ray analyses suggested the title phase to have a narrow homogeneity range. The substructure of Zn13(CrxAl1–x)27 shows close resemblance with the Mn3Al10 structure type. A bonding analysis, through crystal orbital Hamiltonian populations (COHPs), of “Cr9Al18Zn13” as a representative composition indicated that both homo- and heteronuclear interactions are important for the stability of this new phase.
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