NATURE OF DOPED ELECTRONS IN ND2-XCEXCUO4 - ELECTRONIC BAND STRUCTURES OF ND2CUO4 TYPE LA2CUO4, CE2CUO4 AND TH2CUO4

One-electron energy band structures for La2CuO4, Ce2CuO4 and Th2CuO4 with the Nd2CuO4 type crystal structure were calculated by the self-consistent APW method with the local density approximation. The bonding-antibonding splitting between the Cu 3d(x2-y2) and O 2p states on the CuO2 plane makes a pair of sub-bands. In La2CuO4, the Fermi energy cuts the middle of antibonding band resulting in the half-filled band. By replacing La with tetravalent Th, the Cu 3d states raise due to the increase in the number of Cu 3d electron but the bonding band made from Th 6d(3z2-r2) state falls down. In Ce2CuO4, the Fermi energy cuts the bottom of 4f bands. To raise the 4f states, a correction is introduced to the Ce potential and then Ce becomes nearly tetravalent resulting in similar band structure to that of Th2CuO4. By considering the strong correlation in the Cu 3d(x2-y2) state, the doped electrons in Nd2-xMxCuO4 (M = Ce, Th) are thought to be injected into the M d(3z2-r2) bonding band. © 1990, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.