ELECTRONIC-STRUCTURE AND LOCAL CHARGE-DENSITY WAVE IN BA1-XKXBIO3

Bal1-xKxBiO3 becomes metallic and supraconducting at x ~ 0.35. We examine the stability of Bal-,&Bi03 against a local charge density wave formation. Electron-phonon interaction A, on site U and intersite V electron-electron interactions are taken into account. We find that two sets of parameters λ ≥0,7 U>0, V>0 or λ≤0.7, U<0, V<0 can reproduce the optical gap of 2 eV of the insulating BaBi03 compound and the critical concentration 0.35 of the doping leading to a metal-insulating transition. The second set of parameters seems the most reasonable in view of experimental results, i.e. negative U and small electron-phonon interaction. At ≥ 0.4 the bismuth sites are nearly equivalent and there is a single conduction band, less than half-full which is consistent with the featureless optical conductivity spectrum and negative Hall coefficient of the metallic phase. © 1990 IOP Publishing Ltd.