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Hybrid exchange-correlation functional determined from thermochemical data and ab initio potentials.

Wilson, P. J. and Bradley, T. J. and Tozer, D. J. (2001) 'Hybrid exchange-correlation functional determined from thermochemical data and ab initio potentials.', Journal of chemical physics., 115 (20). pp. 9233-9242.

Abstract

Multiplicative potentials, appropriate for adding to the non- multiplicative fractional orbital exchange term in the Kohn- Sham equations, are determined from correlated ab initio electron densities. The potentials are examined graphically and are used in conjunction with conventional thermochemical data to determine a new hybrid exchange-correlation functional, denoted B97-2. Calculations using B97-2 are compared with those from (a) the B97-1 functional [J. Chem. Phys. 109, 6264 (1998)], which has the same functional form and fraction of orbital exchange, but was fitted to just thermochemical data; and (b) the widely used B3LYP functional [J. Chem. Phys. 98, 5648 (1993)]. B97-2 atomization energies are close to those from B97-1; total electronic energies and ionization potentials are less accurate, but remain an improvement over B3LYP. Molecular structures from all three functionals are comparable. Static isotropic polarizabilities improve from B3LYP to B97-1 to B97-2; the B97-2 functional underestimates experimental values, which is consistent with the neglect of zero-point vibrational corrections. NMR shielding constants-determined as the conventional second derivative of the electronic energy- improve from B3LYP to B97-1 to B97-2. Shieldings determined directly from these DFT electron densities using the recently proposed MKS approach [Chem. Phys. Lett. 337, 341 (2001)] are two to three times more accurate than the conventional shieldings, and exhibit an analogous improvement across the three functionals. Classical reaction barriers for sixteen chemical reactions improve significantly from B3LYP to B97-1 to B97-2. The introduction of multiplicative potentials into semi- empirical hybrid functional development therefore appears beneficial.

Item Type:Article
Full text:PDF - Published Version (115Kb)
Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1063/1.1412605
Publisher statement:Copyright (2001) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. Wilson, P. J. and Bradley, T. J. and Tozer, D. J. (2001) 'Hybrid exchange-correlation functional determined from thermochemical data and ab initio potentials.', Journal of chemical physics., 115 (20). pp. 9233-9242. and may be found at http://dx.doi.org/10.1063/1.1412605
Record Created:19 Apr 2007
Last Modified:26 Apr 2011 15:44

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