ELECTRONIC STATES AND METAL-SEMICONDUCTOR TRANSITION IN BAPB1-XBIXO3

The electronic structure of BaPb1-xBixO3 (BPB) is calculated in the framework of mean field approximation and coherent potential approximation, describing the electronic motion in terms of the extended Hubbard model with two kinds of site-dependent parameters; difference in the on-site energies on Bi and Pb sites and effective on-site interaction due to the oxygen breathing modes. Three characteristic band-shapes are obtained as a function of Bi concentration x; a single band and pseudo-gapped band for metallic phase and two separated bands for semiconducting phase, indicating that x plays a role similar to that of the temperature in the case of the Peierls instability. These results are successfully applied to interpret the main features of metal-semiconductor transition of BPB obtained from optical spectra. © 1990, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.