Tendency towards local spin compensation of holes in the high-T/sub c/ copper compounds

Using an Anderson impurity description of the high-T/sub c/ superconductors, we study the character of the states closest to the Fermi level. In a kind of phase diagram involving the Cu d-d Coulomb interaction (U), the charge transfer energy (Δ), and the hybridization (T), we show under which conditions the singlet, triplet, or delocalized ligand hole states are closest to the Fermi level. For reasonable values of T the lowest-energy hole states are local singlets (1A/sub 1g/) of primarily d9L character for U>Δ and local triplets (3B/sub 1g/) of primarily d8 character for U<Δ