Relationship between the electronic and local structure in BaBi1-xPbxO3 and Ba1-xKxBiO3 perovskites

Starting from 2D Peierls-Emery Hamiltonian in the hole representation the relationship between the electronic and local structure in BaBi1-xPbxO3 and Ba1-xKxBiO3 perovskites has been investigated. I attempt to provide some grounding in the model of charge disproportionation: 2Bi(+4)--> Bi+3 + Bi+3(L) under bar(2). Calculated local structure of parent BaBiO3 agrees reasonably well with those supplied by XAFS and XRD measurements. Both breathing 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.