Towards a formal definition of static and dynamic electronic correlations

摘要

Some of the most spectacular failures of density-functional and Hartree-Focktheories are related to an incorrect description of the so-called staticelectron correlation. Motivated by recent progress on the N-representabilityproblem of the one-body density matrix for pure states, we propose a way toquantify the static contribution to the electronic correlation. By studyingseveral molecular systems we show that our proposal correlates well with ourintuition of static and dynamic electron correlation. Our results bring out theparamount importance of the occupancy of the highest occupied naturalspin-orbital in such quantification.