IMPORTANCE OF THE INTERLAYER TE...TE CONTACTS ON THE ELECTRONIC-STRUCTURE OF THE LAYERED TELLURIDE NB3GE0.9TE6

The electronic structure of the layered telluride Nb3Ge0.9Te6 was examined by performing tight-binding band calculations on the stoichiometric composition Nb3GeTe6. Due to the short interlayer Te...Te contacts, the top part of the Te p(z)-block bands of Nb3GeTe6 is raised above the Fermi level. This gives rise to a partial p --> d electron transfer and to positive overlap populations for the interlayer Te...Te contacts, as in the case of the CdI2-type ditellurides MTe2 (M = Ti, Nb). The Fermi surfaces calculated for Nb3GeTe6 suggest that Nb3Ge0.9Te6 is a three-dimensional metal, with its electrical conductivity increasing along the b < c < a axis directions.