Transferability of the partial-wave increments to the second-order pair correlation energies for atoms

Abstract

Partial-wave (PW) increments to the second-order pair correlation energies for K-, KL- and L-shell symmetry-adapted pairs are analysed in order to lay down some rules governing their transferability properties. The changes of the PW increments for members of isoelectronic series (Z dependence) and for sequences of systems with fixed nuclear charge and varying numbers of electrons (N dependence) are discussed. It is found that when considering the transferability properties a distinction has to be made between the contributions defined by the PW that have to be orthogonalised to the occupied Hartree-Fock orbitals (OPW), and the remaining ones (FPW). When analysing the N dependence it is found that the FPW increments increase very slowly and monotonically for increasing N. For dynamical pairs the FPW increments can be considered to be transferable in most practical applications. As a result, when evaluating pair energies for larger systems, one can use the FPW increments obtained for the most simple ion containing the pair considered; this leads to a considerable reduction of computational effort.