Relationship between the electronic and local structure in BaPbxBi1-xO3 and Ba1-xKxBiO3 perovskites

Starting from 2D Peierls-Emery Hamiltonian in the hole representation the r elationship between the electronic and local structure in BaPbxBi1-xO3 and Ba1-xKxBiO3 perovskites has been investigated. I attempt to provide some gr ounding in the model of charge disproportionation: 2Bi(+4) --> Bi+3 + (Bi+3 L2). The O K- and Bi L-3-EXAFS as well as the XPS were calculated and compa red to experimental data. Calculated local structure of parent BaBiO3 agree s reasonably well with those supplied by EXAFS and XRD measurements. Both b reathing and tilting distortions of the Bi-O bonds were found. Evolution of the local structure with hole (electron) doping was evaluated numerically and compared with EXAFS data. The low-temperature "anomalies" in the local structure of BaBiO3 are discussed. (C) 2000 Elsevier Science B.V. All right s reserved.