A global approach to perform large-scale configuration-interaction calculations

We present a global approach that allows one to tackle cumbersome configuration-interaction calculations. The method is based on the use of approximate configuration-averaged Hamiltonian matrix elements that can be expressed in compact form as a combination of Slater integrals.With some assumptions, we show that the Hamiltonian matrix to be diagonalized may be reduced to a size equivalent to the number of configurations in the basis set. The approach can be used to estimate shifts of configuration average energies and changes in the total strength of transition arrays. The method is also well suited to work out roughly difficult configuration-interaction calculations, to determine the minimal set of interacting configurations to be used in actual fine-structure calculations. (author)