Fermi-surface study of Ba1ÀxKxBiO3

We present all-electron computations of the three-dimensional ~3D! Fermi surfaces ~FS’s! in Ba12xKxBiO3 for a number of different compositions based on the self-consistent Korringa-Kohn-Rostoker coherentpotential-approximation approach for incorporating the effects of Ba/K substitution. By assuming a simple cubic structure throughout the composition range, the evolution of the nesting and other features of the FS of the underlying pristine phase is correlated with the onset of various structural transitions with K doping. A parametrized scheme for obtaining an accurate 3D map of the FS in Ba12xKxBiO3 for an arbitrary doping level is developed. We remark on the puzzling differences between the phase diagrams of Ba12xKxBiO3 and BaPbxBi12xO3 by comparing aspects of their electronic structures and those of the end compounds BaBiO3 , KBiO3, and BaPbO3. Our theoretically predicted FS’s in the cubic phase are relevant for analyzing highresolution Compton scattering and positron-annihilation experiments sensitive to the electron momentum density, and are thus amenable to substantial experimental verification.