Calculations of the electronic structure and superconducting properties of the Ba(K)Pb(Bi)O3 system.

We have performed band-structure calculations of the cubic perovskites BaPbO{sub 3}, BaBiO{sub 3}, and KBiO{sub 3} by the augmented-plane-wave (APW) method. Using the APW results, we have constructed the first realistic tight-binding (TB) Hamiltonians for these materials including the {ital s} (Ba or K) orbitals, the {ital s} and {ital p} (Pb or Bi) orbitals, and the {ital p} (O) orbitals. These TB Hamiltonians were used to apply the coherent-potential approximation to study disorder effects. We found that, while the position of the Fermi level moves qualitatively according to the rigid-band approximation, the oxygen-dominated bandwidth widens as a result of alloying either on the Ba or the Bi sites. Our evaluation of the electron-phonon coupling indicates that this is a possible mechanism to explain superconductivity in these systems.