Investigation of Hole Distribution in Y_1-xPr_xBa₂Cu₃O₇

The electronic structure of Y_1-xPr_xBa₂Cu₃O₇ is described by a tight-binding Hamiltonian in which the Pr-O hybridization and the 2p_σ - 2p_π Coulomb repulsion are taken into account. The dependence of planar hole-density, localized hole-density and chemical potential of holes on Pr concentration is calculated by a coherent potential approximation. The result shows that the insensitivity of hole-density on the CuO₃ chains with the Pr-doping is due to the 2p_σ - 2p_π repulsion. Some other experimental facts can also be well interpreted.