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PW86-PW91 density functional calculation of vertical ionization potentials: Some implications for present-day functionals

TitlePW86-PW91 density functional calculation of vertical ionization potentials: Some implications for present-day functionals
Publication TypeJournal Article
Year of Publication2001
AuthorsShapley, WA, Chong, DP
JournalInternational Journal of Quantum Chemistry
Volume81
Pagination34-52
Date PublishedJan
Type of ArticleArticle
ISBN Number0020-7608
KeywordsACCURATE, AROMATIC MOLECULES, CORRELATED MOLECULAR CALCULATIONS, DFT, EXCHANGE-ENERGY, functionals, GAUSSIAN-BASIS SETS, HE(II) PHOTOELECTRON-SPECTRA, ionization potential, ORGANIC-MOLECULES, PHOTO-ELECTRON SPECTRA, PW86, PW91, SPECTROSCOPY, WAVE-FUNCTIONS
Abstract

A total of 181 vertical ionization potentials (VIPs) of 41 molecules were calculated by density functional theory (DFT) employing the Perdew-Wang 1986 (PW86) exchange and Perdew-Wang 1991 (PW91) correlation functionals and using the aug-cc-pV5Z basis and experimental ground-state geometries. The overall average absolute deviation (AAD) from experiment was found to be 0.55 eV and only 0.31 eV for linear molecules but 0.86 eV for nonplanar molecules. A number of VIPs were in error by over 2 eV. In particular, DFT performed most poorly when ionization was from an orbital with highly varying density gradients (which arise from the orbital’s shape or compactness or through its density being distributed over a number of atoms). Indications are that many or all present-day functionals suffer from the same failings. (C) 2001 John Wiley & Sons, Inc.

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