Ground state energies of various lighter atoms and few heavy atoms are calculated using Hartree-Fock method’s several variants. Obtained results were compared with previous theoretical and numerical computations for the ground state energies of investigated atoms. It is found upon comparison that the energy differences are lying between 15μ Hartree to 0.35 Hartree for RHF, UHF, ROHF methods (non-relativistic) while 79μ Hartree to 252 Hartree for DHF method. Furthermore, differences of DHF energies and NIST data are also calculated and are found in range 15μ Hartree to 10.6 Hartree. The results suggested that Hartree-Fock method with its underlying approximation is suitable in estimating ground state energies and relativistic effects turn out to be important in case of heavier atoms.

Index Terms- Correlation effects, Hartree-Fock method, open and closed shell systems, Self-consistent fields.