  Coulomb interactions that occur in electronic structure calculations are
correlated by allowing basis function components of the interacting densities
to polarize, thereby reducing the magnitude of the interaction. Exchange
integrals of molecular orbitals are not correlated. The modified Coulomb
interactions are used in single-determinant or configuration interaction
calculations. The objective is to account for dynamical correlation effects
without explicitly introducing higher spherical harmonic functions into the
molecular orbital basis. Molecular orbital densities are decomposed into a
distribution of spherical components that conserve the charge and each of the
interacting components is considered as a two-electron wavefunction embedded in
the system acted on by an average field Hamiltonian plus . A method of avoiding
redundancy is described. Applications to atoms, negative ions and molecules
representing different types of bonding and spin states are discussed.
