PW86–PW91 Density Functional Calculation of Vertical Ionization Potentials: Some Implications for Present-Day Functionals

January 1, 2001

Journal Article

PW86–PW91 Density Functional Calculation of Vertical Ionization Potentials: Some Implications for Present-Day Functionals

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 performedmost 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.

Revised: January 23, 2012 | Published: January 1, 2001

Citation

Shapley W.A., and D. Chong. 2001. PW86–PW91 Density Functional Calculation of Vertical Ionization Potentials: Some Implications for Present-Day Functionals. International Journal of Quantum Chemistry 81, no. 1:34-52.