Improvement of multiconfigurational wave functions and energies by correlation energy functionals

Several aspects of hybrid methods resulting from combining multiconfigurati onal (MC) wave functions with correlation energy functionals are discussed, in particular for a family of functionals recently proposed.(1,2) It is fo und that adding the correlation at the end of a MC calculation instead of i ncluding it in the self-consistent procedure constitutes an excellent appro ximation. MC potential energy curves and spectroscopic constants show a sig nificant improvement after being corrected with correlation energies from t his family of functionals.