Performance of DFT Sergio Aragon San Francisco State University CalTech PASI January 4-16, 2004

H2 Dissociation Curve

Performance: Ozone

Bond lengths & Bond Angles Koch & Holthausen

Octahedral Cr Complex

Octahedral Metallic Carbonyls

Vibrational Frequencies

Thermochemistry

Ionization Energies HF under-estimates ionization energies: more correlation in the neutral than in the ion.

Electron Affinities Affinities are very problematic for HF//anything methods. Extra electron adds correlation and is very diffuse. DFT does reasonably well.

Excitation Energies: Ethylene Poor asymptotic behavior of ordinary functionals yields a deteriorating picture as the excitation energy increases. Asymptotically corrected functionals such as PBE perform as well as the very expensive CAS methods.

Dipole Moments HF predicts the wrong sign of the dipole moment for CO! DFT performs very well.

Polarizabilities Polarizabilities are inversely proportional to orbital energy differences. DFT, with poor asymptotics, has high values of the HOMO energy and overestimates the polarizability.

Hydrogen bonding: Water Dimer The fabulous numbers for the BLYP functional have been shown to be due to fortuitous error cancellation. Hybrid functionals do not overperform the HF//MP2 level.

Further Study Koch, W. and Holthausen, M.C., “A Chemist’s Guide to Density Functional Theory”, Wiley-VCH: New York, 2000. Further comparisons are available on: IR intensities NMR chemical shifts and spin-spin couplings Hyperpolarizabilities ESR tensors & Hyperfine couplings Weakly bound systems & clusters.

Atoms in Molecules