title: Homoatomic stella quadrangula [Tl8]6- in Cs18Tl8O6, interplay of spin-orbit coupling, and Jahn-Teller distortion.
abstract: Cs(18)Tl(8)O(6) was synthesized reacting the binary compounds CsTl and Cs(2)O. According to single crystal X-ray analysis, the title compound crystallizes as a novel structure type in the cubic space group I23 and is diamagnetic. The electronic structure of the extended solid and of excised Cs(6)Tl(8) clusters has been examined by relativistic density functional calculations including spin-orbit coupling. Cs(18)Tl(8)O(6) comprises a clusteranion [Tl(8)](6-) in the shape of a tetrahedral star. An isoelectronic cluster was found previously in Cs(8)Tl(8)O, however, with the shape of a parallelepiped. Both clusteranions can be derived from a homocubane unit by displacive distortions. It has been shown by quantum mechanical analyses that the closed-shell electronic structure of the parallelepiped is the result of a Jahn-Teller distortion, while in contrast the tetrahedral star in Cs(18)Tl(8)O(6) would still exhibit an open-shell degenerate HOMO within a scalar relativistic approximation. Only if spin-orbit coupling is considered, a closed-shell electronic system is obtained in accordance with the diamagnetic behavior of Cs(18)Tl(8)O(6).
authors: Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany.
authors: Ulrich
authors: U
authors: Wedig
authors: Vyacheslav
authors: V
authors: Saltykov
authors: Jürgen
authors: J
authors: Nuss
authors: Martin
authors: M
authors: Jansen