Are Ba11Cd6Sb12 and Sr11Cd6Sb12 Zintl phases or not?: A density-functional theory study

The chemical bonding and the electronic band structures of two isoelectronic and isostructural Zintl compunds, Sr11Cd6Sb12 and Ba11Cd6Sb12, have been studied on the basis of the density-functional theory (DFT) using the tight-binding linear-muffin-tin-orbital (TB-LMTO-ASA) approach and the local-density approximation (LDA). These results reveal that the classic Zintl reasoning and the concept of two-center two-electron bonds cannot explain the subtlelies of this complex structure type. the computations also suggest that the antimony dimers present in these structures play an important role and allow for a greater flexibility in optimization of the bonding with the surrounding d-metal atoms. (C) 2008 Wiley Periodicals, Inc.