Interaction energies of van der Waals and hydrogen bonded systems calculated using density functional theory: Assessing the PW91 model

The performance of density functional theory using the Perdew and Wang's ex change and correlation functionals (PW91) functional for the prediction of intermolecular interaction energies is evaluated based on calculations on t he neon, argon, methane, ethylene, and benzene dimers, as well as on 12 hyd rogen bonded complexes (water, methanol, formic acid, hydrogen fluoride, am monia, formamide dimers and water-methanol, water-dimethyl ether, water-for maldehyde, hydrogen cyanide-hydrogen fluoride, water-ammonia, water-formami de complexes). The results were compared with those obtained from Becke's e xchange and Lee, Yang, and Parr's correlation functionals (BLYP), Becke's 3 parameter functional combined with Lee, Yang, and Parr's correlation funct ional (B3LYP), second order Moller-Plesset perturbation (MP2), and coupled cluster calculations with single and double substitutions and with non-iter ative triple corrections [CCSD(T)] calculations. The calculated interaction energies show that the PW91 functional performs much better than the BLYP or B3LYP functionals. The error in the computed binding energies of the hyd rogen bonded complexes is 20% in the worst case. The most demanding cases a re the systems with large dispersion contributions to the binding energy, s uch as the benzene dimer. In contrast to the BLYP and B3LYP functionals whi ch fail to account for dispersion, the PW91 functional at least partly reco vers the attraction. The basis set dependence of the PW91 functionals is re latively small in contrast to the MP2 and CCSD(T) methods. Despite its occa sional difficulties with dispersion interaction, the PW91 functional may be a viable alternative to the ab initio methods, certainly in situations whe re large complexes are being studied. (C) 2001 American Institute of Physic s.