Calculations of the electronic structure and superconducting properties of the Ba(K)Pb(Bi)O3system

We have performed band-structure calculations of the cubic perovskites ${\mathrm{BaPbO}}_3$, ${\mathrm{BaBiO}}_3$, and ${\mathrm{KBiO}}_3$ 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 s (Ba or K) orbitals, the s and p (Pb or Bi) orbitals, and the 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.