Density-functional thermochemistry. III. The role of exact exchange

TLDR

Kohn–Sham density‑functional theories with gradient corrections achieve remarkable thermochemical accuracy, yet further improvements are unlikely without incorporating exact‑exchange information. The study aims to demonstrate that exact‑exchange contributions are essential for advancing thermochemical predictions. To support this claim, the authors develop a semiempirical exchange‑correlation functional that combines local‑spin‑density, gradient, and exact‑exchange terms and test it on 56 atomization energies, 42 ionization potentials, 8 proton affinities, and 10 total atomic energies of first‑ and second‑row systems.

Abstract

Despite the remarkable thermochemical accuracy of Kohn–Sham density-functional theories with gradient corrections for exchange-correlation [see, for example, A. D. Becke, J. Chem. Phys. 96, 2155 (1992)], we believe that further improvements are unlikely unless exact-exchange information is considered. Arguments to support this view are presented, and a semiempirical exchange-correlation functional containing local-spin-density, gradient, and exact-exchange terms is tested on 56 atomization energies, 42 ionization potentials, 8 proton affinities, and 10 total atomic energies of first- and second-row systems. This functional performs significantly better than previous functionals with gradient corrections only, and fits experimental atomization energies with an impressively small average absolute deviation of 2.4 kcal/mol.