New possibilities of Möller-Plesset perturbation theory for calculating correlation energies of closed-shell systems

A new scheme for generating and selecting configurational wave functions (CWF) including the correlation effects is suggested. Standard Möller-Plesset perturbation theory (SMP) is modified in such a way that the newly constructed CWF and the Hartree-Fock reference determinant are the eigenfunctions of a zero-order Hamiltonian. Possessing all advantages of SMP, the calculation scheme allows for more than 80% of the empirical correlation energy in the second order. The results for diatomic hydrides are comparable in accuracy to those obtained by the configuration interaction method.