ELECTRONIC-STRUCTURE OF AG5PB2O6

The results of tight-binding calculations on the subvalent silver-rich oxide Ag5Pb2O6 indicate that the correct valence state. formulation i s (3)(infinity)[Ag-5](Pb24+O62-)-Pb-4+. The odd electron per formula u nit in [Ag-5](4+) is delocalized over the entire silver substructure, namely over both the silver atoms making up the Kagome layer and those of the chains which are threaded through it. Although this state of a ffairs results in a half-filled silver s band at the Fermi level, the structure does not distort to lower symmetry because of the three-dime nsional nature of the Fermi surface. Both the electronic density of st ates and the Fermi surface, although complicated, may be readily under stood as a combination of contributions from the layer and chain atoms of the silver substructure. It is suggested that doping the material with fluorine (to give Ag5Pb2O5F) should be a good test of the half-fi lled band for the oxide, since filling it with one more electron shoul d lead to a semiconductor.