Semiempirical determination of ionisation potentials, term values and correlation energies of third-row transition-metal atoms by vertical analysis

A simple semiempirical model is proposed for estimating correlation energies by vertical analysis. It is tested on first-row atoms and then applied to transition-metal atoms. Experimentally unknown ionisation potentials of Cr, Mn and Fe are determined with an accuracy of 0.1 eV. Furthermore, unknown term values and electron affinities are estimated. The pair parentage coefficients needed in this work are tabulated. Relativistic energy corrections for transition-metal atoms are also given. The correlation energies are also discussed.