Studies on AB(2)-type intermetallic compounds .1. Mg2Ge and Mg2Sn: Single-crystal structure refinement and ab initio calculations

The crystal structures of the two Zintl phases Mg2Ge and Mg2Sn have been refined using single-crystal X-ray data (anti-CaF2 type; Mg2Ge: a = 6.3849(4) Angstrom, R1 = 0.0149, wR2 = 0.0194; Mg2Sn: a = 6.7594(4) Angstrom, R1 = 0.0066, wR2 = 0.0165). Moreover we performed state-of-the-art ab initio calculations within the framework of density functional theory (DFT), in connection with the local density approximation (LDA) and scalar-relativistic, norm-conserving pseudopotentials. We calculated the structural and electronic properties of Mg2Ge and Mg2Sn, and obtained the valence charge transfer by applying the method of zero-flux surfaces. We found that a large charge transfer exists, but not as large as predicted by the Zintl-Klemm-Busmann concept.