F. Sasaki and M. Yoshimine
Phys. Rev. A 9, 17 – Published 1 January 1974
I. Correlation energies of B, C, N, O, F, and Ne
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.
DOI:https://doi.org/10.1103/PhysRevA.9.17
©1974 American Physical Society
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II. Electron affinities of B, C, N, O, and F
ABSTRACT
Extensive configuration-interaction calculations have been carried out to determine electron affinities of the first-row atoms, B to F. Calculated electron affinities in eV with the observed values in parentheses are 0.15, 1.11(1.25), -0.52, 1.13(1.461), and 3.12(3.448), for B, C, N, O, and F, respectively. Our best estimates, based on an empirical extrapolation which makes use of the known C, O, and F affinities, for B and N electron affinities are 0.24 and -0.19 eV, respectively. Detailed analysis of the results in terms of contributions from various classes of configurations shows that the K-shell and KL-intershell correlation-energy contributions to these electron affinities are negligibly small, and that about 15% of the total correlation contribution comes from the triple and higher electron-excitation configurations. Symmetry-adapted pair-correlation calculations have been carried out for O, O−, F, and F− to study convergence patterns for the correlation energy and electron affinity with respect to the orbital basis used to construct the configurations. Such pair-correlation calculations are known to overcompute the correlation energy. The excess energies, which correspond to pair-pair interaction energies neglected in the pair-correlation calculations, were roughly constant over a range of orbital basis sizes, with magnitudes about twice the energy contributions from the configurations of triple and higher excitations omitted in the pair-correlation calculations. Accordingly, this approximation should overestimate the electron affinity if a complete orbital basis is used.
DOI:https://doi.org/10.1103/PhysRevA.9.26
©1974 American Physical Society
To download the article click on the following link:
https://journals.aps.org/pra/abstract/10.1103/PhysRevA.9.26
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