Improved ground state energies of electronegative atoms using Hartree–Fock self-consistent field approximation

In many-electron systems, the exchange and correlation energies, associated with the indistinguishability and Columbic interactions among electrons, are the major cause for the inaccurate estimate of their ground state energies. In the present study, improved ground state energies of highly electronegative atoms such as F, Cl, B, Al and Sc are obtained using unrestricted Hartree–Fock method, though Hartree–Fock method does not incorporate the interactions between electrons (correlation) leading to inaccurate estimates of total energy. Nevertheless, an augmented correlation-consistent polarized valence Quintuple-Zeta functions (aug-cc-pV5Z) are used which incorporate the correlation and polarization effects in the functions. Such effects are very important in case of highly electronegative atoms. The results obtained in this study are compared with previous theoretical work and with values given in NIST tables for the ground state energies of the investigated atoms. It has been found that energies have been much improved by using aug-cc-pV5Z basis sets for the atoms under investigation.