Study of electronic structures in LaCo1-xTixO3 (x=0,0.05 and 0.15) using discrete-variational-X alpha cluster method

Electronic structures of [CoO6](9-) clusters have been studied by ab initio molecular-orbital (MO) calculations using the discrete-variational (DV)-X alpha cluster method in order to investigate the correlation between the ch ange in the type of the majority carrier and electronic structures in LaCo1 -xTixO3 (x = 0, 0.05 and 0.15). The most significant features are that the e(g up arrow) bandwidth in the x not equal 0 specimen is wide in comparison with the x = 0 specimen and the Co-O bonding MO energy levels in the x not equal 0 specimens are in the energy range of -3 eV to -2 eV. These calcula tions indicate that both the 3d electrons in donor centers of sigma* bands and the O 2p ligand holes in sigma* bands are responsible for the electroni c conduction in the x = 0.05 and x = 0.15 specimens but the competition bet ween the densities of 3d electrons in sigma* bands and O 2p ligand holes do minates the type of the majority carrier.