Electronic Structure of the Ba sub (n+1) Pb sub n O sub (3n+1) Homologous Series.

A combination of linear augmented-plane-wave and Tight-Binding (TB) techniques has been applied to calculate the electronic band structures of selected members of the Ba sub (n+1) Pb sub n O sub (3n+1) homologous series. The results show that the two end members of this series, Ba sub 2 PbO sub 4 (n=1) and BaPbO sub 3 (n=inf), exhibit semiconducting and metallic properties, respectively. The calculated (~ 1.7 eV) semiconductor gap in Ba sub 2 PbO sub 4, which has the K sub 2 NiF sub 4 -type structure, is due to nearest-neighbor (sp sigma) interactions between Pb(6s) and O(2p) orbitals at the apical sites. TB calculations for intermediate members of this series show that this gap vanishes for the n = 3 phase, Ba sub 4 Pb sub 3 O sub 10, yielding semimetallic behavior. A detailed analysis of the electronic properties of this system suggests related compounds which are promising candidates for high-temperature superconductivity.