A comparative analysis of Hartree-Fock and Kohn-Sham orbital energies

Abstract

Hartree-Fock and Kohn-Sham orbital energies, the latter computed with several dierent exchange/ correlation functionals, are compared and analyzed for 12 molecules. The Kohn-Sham energies dier signi®-cantly from experimental ionization energies, but by amounts that are, for a given molecule and exchange/ correlation functional, roughly the same for all of the valence orbitals. With the exchange/correlation functionals used, the energy of the highest occupied KohnSham orbital does not approximate the corresponding ionization potential any better than do the other orbital energies.

A Joint Photoelectron Spectroscopy and Theoretical Study on the Electronic Structure of UCl5− and UCl5

“…The ADE of 4.76 eV observed for UCl 5 À is much higher than that of UF 5 À (3.885 eV), [32] indicating that UCl 5 À is highly electronically stable in the gas phase. [33,34] Our previous experimental and theoretical results indicate that Koopmans theorem holds approximately in molecules like uranyl halides [29,30] with aspects to the trend and the ordering of VDEs, although an overall energy shift is needed to compare with the experiment. This detachment channel was observed to have very low cross-sections in the case of UF 5 À and was not clearly observed because of the overlap with the X band.…”

“…Prior theoretical studies showed that Kohn-Sham orbitals and their orbital energies can be useful in the qualitative interpretation of electron detachments and spectroscopy properties. [33,34] Our previous experimental and theoretical results indicate that Koopmans theorem holds approximately in molecules like uranyl halides [29,30] with aspects to the trend and the ordering of VDEs, although an overall energy shift is needed to compare with the experiment. In heavy metal complexes, state-specific methods with inclusion of SO effects are needed to accurately account for state energies.…”

Investigation on the absolute and relative photoionization cross sections of 3 potential propargylic fuels

“…This has been shown to cause an underestimation, up to several electron volts, in the approximation of the first ionization energy from the HOMO energy . However, their use in determining excitation energies for excited electronic states as the difference in orbital energies has been shown to be reliable …”

DFT study of ionization potentials for aza‐substituted aromatic rings

“…Kohn–Sham orbitals should include the component of electron correlation. Although the meaning of the Kohn–Sham “one‐electron” orbitals 21, section 7‐6 of Ref. 5 of B3LYP method is not clear, Politzer and Abu‐Awwad 21 found that Kohn–Sham orbital energies differ significantly from experimental ionization potentials for some small systems.…”

“…Although the meaning of the Kohn–Sham “one‐electron” orbitals 21, section 7‐6 of Ref. 5 of B3LYP method is not clear, Politzer and Abu‐Awwad 21 found that Kohn–Sham orbital energies differ significantly from experimental ionization potentials for some small systems. Salzner et al 22 studied polyenes and big π‐orbital aromatic ring systems with this methodology and found that the IPs (negative highest occupied molecular orbitals [HOMO] energies) are closer to experimental values when using hybrid functionals.…”