Go to MO65to visualize the evolution of charge density as the MO's are filled. The SCF problem for the neutral Cu₄O₄ lamella in the crystal field of an infinite layer in a superconducting cuprate (see Acrivos and Stradella, Int. J. Quantum Chemistry, 46, 55 (1993)) involves (8+29)*4=74*2 electrons moving in the fiield of the nuclei and point charges from the crystal field. The highest filled HFMO is MO74 and the lowest unfilled LUMO is MO75. Neither the valence of the Cu nor the O atoms in the cluster are fixed by the SCF calculation. The reader is asked to go over the lower filled LFMO to reckon the importance of the oxygen atomic orbitals in the conduction band states of the CuO₂ layer, assumed to carry all the current. MO63 has very little contribution from the O atomic orbitals. The electron density has more physical significance in this approach.