Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

Within the Generalized Exchange (GX) LSD scheme, a method to calculate the ionization potential (IP) of an atom has been developed involving correction terms to the negative of the eigenvalue of the highest occupied atomic orbital (HOAO). These correction terms are evaluated non-iteratively using the fully occupied orbitals of the ground state of the neutral atom. Within the unrelaxed orbital approximation, this corrected eigenvalue IP, IP^corr, is completely equivalent to the Transition State IP, calculated from an SCF calculation at half-occupancy of the HOAO, when used with density-functional (DF) schemes that do not include self-interaction. The present scheme can also be used with self-interaction corrected DF schemes. In both cases, the corrected eigenvalue method of calculating IP's gives good results. The techniques used to derive IP^corr are applied to derive an expression for the electronegativity of the free atom which can be used with both self-interaction and non-self-interaction corrected DF schemes. The results of IP and electronegativity calculations for the helium to krypton atoms are reported using a variety of DF schemes. These are compared to each other and to the experimental values whenever possible.