A size-extensive modification of super-CI for orbital relaxation

A size-extensive modification is proposed for the configuration interaction with the Hartree-Fock (HF) reference plus single excitations (super-CI) for the orbital relaxation, where a partial renormalization is utilized. The way of renormalization owes to Ahlrichs's coupled pair functional. This proposal is named concurrent electron relaxation functional (CERF). The size-extensivity and performance of CERF are checked through test calculations.