PAIR CORRELATION ENERGIES FOR THE 3D SHELL

Pair energies contributing to the all-external correlation energies of the 3d electrons are computed for the Zn2+ closed-shell ion by means of second-order perturbation theory starting with the sum of one-electron Hartree-Fock operators as the zeroth-order Hamiltonian. The variation- perturbation symmetry-adapted pair functions are taken in the form of partial-wave expansions. The results for the pair energies and total correlation energy are compared with related theoretical and semiempirical results. Our analysis indicates that nondynamical correlation effects are of little importance in the ground states of transition metal systems.