Density-functional thermochemistry. II. The effect of the Perdew-Wang generalized-gradient correlation correction

Becke, Axel D.

AA(Department of Chemistry, Queen's University, Kingston, Ontario, Canada K7L 3N6)

The Journal of Chemical Physics, Volume 97, Issue 12, December 15, 1992, pp.9173-9177

Abstract

In an earlier paper [A. D. Becke, J. Chem. Phys. 96, 2155 (1992)], Kohn-Sham density-functional calculations of the total atomization energies of the 55 molecules of the Gaussian-1 database of Pople and co-workers [J. Chem. Phys. 90, 5622 (1989); 93, 2537 (1990)] were reported. We found that the local-spin-density exchange-correlation approximation with a ``gradient correction'' for exchange gave an average deviation from experiment of only 3.7 kcal/mol. In the present work we assess the role of gradient corrections for dynamical correlation, and we enlarge our earlier survey to include 42 atomic and molecular ionization potentials and 8 proton affinities as well. We conclude that gradient corrections for correlation do not improve atomization energies, but are vitally important in electron nonconserving processes such as ionization.


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