The Electronic Structure of DyGe3

Recently the crystal structure of a germanium-rich dysprosı́um germanide (DyGe3) has been reported. Significant bonding interactions are present between the germanium atoms in the structure. One type of germanium forms kinked infinite chains 1x[Ge]. The remaining two germanium atoms form dimers, stacked in a two-dimensional array as 2x[Ge2]. DyGe3raises intriguing questions concerning stability and bonding; these are investigated with the aid of extended Hückel calculations. Ge atoms receive electrons from Dy, and Ge states dominate below the Fermi level. There is an interesting electron balance between the two Ge sublattices. The Ge2layers contain one additional electron, making them formally a Ge-2double layer; the one-dimensional Ge chains contain two extra electrons, fitting the typical Zintl picture as Ge2-. The Ge2double layers exhibit two-center bonding in the pairs, perpendicular to an electron deficient multicenter bonding system within the layers. The latter is responsible for the expected two-dimensional metallic conductivity.