Electronic structures of Nd₂CuO₄ and its electron-doped cluster systems

First principles multi-configuration self-consistent field calculations are performed for the electronic states of NdCuO systems, taking a Cu₂O₇ cluster as a model. We show that, in the undoped system, electrons localized in Cu d_x²-y² orbitals interact antiferromagnetically with an exchange coupling constant of 0.28 eV and that, in the electron-doped system, a dopant electron is accomodated in the Cu 4s bonding orbital.