| Abstract
| - A Koopmans-like approximation is introduced in the spin-polarized version of the Kohn−Sham (KS) densityfunctional theory to obtain a relation between KS orbital energies and vertical ionization potential and electronaffinity. Expressions for reactivity indexes (like electronegativity, hardness, electrophilicity, and excitationenergies) include KS frontier orbital energies and additional contributions associated with the self-interactioncorrection. Those reactivity parameters were computed with different exchange-correlation functionals totest the approach for a set of small molecules. The results show that the present approximation provides abetter way to estimate hardness, electronegativity, and electrophilicity than just the use of frontier orbitalenergy values. However KS HOMO and LUMO energy gap gives a better agreement with excitation energies.
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