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Abstract

The structural relations of La(2)Sb type compounds and their oxygen stuffed variants, like e. g. Eu(4)Sb(2)O (anti-K(2)NiF(4) type), are discussed. In the course of these investigations, the crystal structures of La(2)Sb, Pr(2)Sb, Sm(2)Sb, Nd(2)Bi, and Sm(4)Bi(2)O were determined and refined from single crystal data. Band structures have been calculated in the framework of density functional theory, and the bonding properties of the individual compounds are compared on the basis of the Electron Localization Function (ELF). Based on specific geometrical parameters, the La(2)Sb type compounds are arranged in a structure field map. Three distinct areas arise: insulating K(2)NiF(4) type compounds, semiconducting, oxygen stuffed variants and oxygen-free metallic compounds. La(2)Sb is found in the latter area, ruling out oxygen content, which is confirmed by high resolution single-crystal X-ray diffraction. The electronic structures of the compounds are related to the valence electron count. Pnictides of tri-valent metals are metallic and feature local multicenter metal-metal bonds, di-valent metals form oxygen stuffed variants. Samarium is the only element which is found in both areas of the structure field map, displaying an oxygen free and a stuffed variant.