Electronic structure of the ${\mathrm{Ba}}_{\mathit{n}+1\mathrm{}}$${\mathrm{Pb}}_{\mathit{n}}$${\mathrm{O}}_{3\mathit{n}+1\mathrm{}}$ 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 ${\mathrm{Ba}}_{\mathit{n}+1\mathrm{}}$ ${\mathrm{Pb}}_{\mathit{n}}$ ${\mathrm{O}}_{3\mathit{n}+1\mathrm{}}$ ho- mologous series. The results show that the two end members of this series, ${\mathrm{Ba}}_2$ ${\mathrm{PbO}}_4$ (n=1) and ${\mathrm{BaPbO}}_3$ (n=∞), exhibit semiconducting and metallic properties, respectively. The calculated (∼1.7 eV) semiconductor gap in ${\mathrm{Ba}}_2$ ${\mathrm{PbO}}_4$, which has the ${\mathrm{K}}_2$ ${\mathrm{NiF}}_4$-type structure, is due to nearest-neighbor (spσ) 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, ${\mathrm{Ba}}_4$ ${\mathrm{Pb}}_3$ ${\mathrm{O}}_{10}$, yielding semimetallic behavior. A detailed analysis of the electronic properties of this system suggests related compounds that are promising candidates for high-temperature superconductivity.