Møller–Plesset theory for atomic ground state energies

Abstract

Abstract Mø–Plesset theory, in which electron correlation energy is calculated by perturbation techniques, is used in second order to calculate energies of the ground states of atoms up to neon. The unrestricted Hartree–Fock (UHF) Hamiltonian is used as the unperturbed system and the technique is then described as unrestricted Mø–Plesset to second order (UMP2). Use of large Gaussian basis sets suggests that the limiting UMP2 energies with a complete basis of s, p , and d functions account for 75–84% of the correlation energy. Preliminary estimates of the contributions of basis functions with higher angular quantum numbers indicate that full UMP2 limits give even more accurate total energies.