Configuration-interaction study of atoms. I. Correlation energies of B, C, N, O, F, and Ne

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Abstract
The configuration-interaction method has been used to calculate the wave functions and energies for the ground state and some selected excited states of the atoms B to Ne. A systematic way of selecting atomic orbital basis and configurations has been developed and is reported in some detail. The calculated total correlation energies range from 95 to 97% of the empirical correlation energy. Calculated term energies of the carbon atom are within 2% of the spectroscopic values. The correlation energies were analyzed in terms of contributions from various classes of configurations, and these contributions were compared with results of previous work. The energy contributions from the class of configurations of triple and higher electron excitations are estimated to be of the order of (3-4)% of the total correlation energy, which is larger than previous estimates of (1-3)% for these atoms.