Core correlation atomization energies

For all results in this paper, spin-orbit coupling corrections have been added to open-shell calculations from a compendium given elsewhere I0) we note that this consistent treatment sometimes differs from the original methods employed by other workers, e.g., standard G3 calculations include spin-orbit contributions only for atoms. In the SAC and MCCM calculations presented here, core correlation energy and relativistic effects are not explicitly included but are implicit in the parameters (i.e., we use parameters called versions 2s and 3s in the notation of previous papers 11,16,18)). 

Table I. ASCF and STS core-level binding energies ( E and lei, respectively ) for free A1 atom, using various exchange and correlation potentials, (all energies are in eV) in comparison witli reference data.

In earlier papers [6-8] we have proposed a procedure for evaluating core ioniza-tion/excitation chemical shifts in molecules from computed core ionization/excitation energies for the relevant isolated atom in neutral and valence-ionized states and from computed charge transfer relative to this atom within the molecule. The atomic calculations involved relaxation, possibly correlation and, when appropriate, relativity and other effects, while in the molecule one could use any approximate method (possibly involving effective core potentials) yielding reliable charges. 

In this paper, we shall present a procedure for evaluating electron relaxation, inner-core correlation, and Breit, qed, and nuc corrections to 2p-core ionization energies and spin-orbit splitting in molecular systems, from tabulated results on atoms from Cl to Ba, excluding transition elements. 

As the relativistic and qed corrections essentially depend on the velocities of the involved electrons, which in turn critically depend on the charge transferred onto or from the core-ionized atom, and as the relaxation and correlation corrections also depend, in a different way, on charge transfer [6-8], one may conjecture that in a molecule all significant corrections to Koopmans energies depend on charge transfer about the ionized atom, and thus on chemically shifted ionization energies, in the same way as for a bare atom they depend on the uncorrected ionization energy. 

---