Electronic- and crystal-structure effects on superconductivity in theBaPb1−xBixO3system

Self-consistent, scalar-relativistic, linear-augmented-plane-wave electronic-structure calculations have been carried out for the $\mathrm{Ba}{\mathrm{Pb}}_{1-x}{\mathrm{Bi}}_x{\mathrm{O}}_3$ system in the cubic ($x=0, 0.3, 1$) and body-centered-tetragonal ($x=0.3\mathrm{}$) phases. The results suggest that the relatively high superconducting transition temperatures ($T_c\approx 13$ K) that are observed for $0.05<~x<~0.3$ are due to strong electron-phonon coupling which arises from modulation of the dominant ($\mathrm{sp}\sigma$) interaction between neighboring Pb-Bi $6s$ and O $2p$ orbitals at $E_F$.