Simple molecular wavefunctions with correlation corrections

It is shown that the main deficiencies of wavefunctions of Hartree-Fock type (wrong dissociation behavior and absence of correlation between electrons of unlike spin) may be corrected by a simple method. Just sufficient CI is admitted to ensure qualitatively correct dissociation, while the short-range correlation energy is estimated with the Colle-Salvetti functional. Potential energy curves for H₂ and LiH are computed at various levels of approximation and the main features of the method are discussed.