A simple scaling for combining multiconfigurational wavefunctions with density functionals

A simple scaling procedure is presented for combining multiconfigurational wavefunctions with density functional estimates of the dynamic electron correlation. It is based on the idea of assigning an average correlation energy to each electron in the system. The procedure is illustrated by application to the potential energy curves of Li2 and F2 using different choices of the number of electrons which are correlated in the reference wavefunction. The method is also applied to calculating the excitation energies of the first-row transition metals (Sc–Cu). Results are presented for four widely used correlation density functionals.