title: Validation of DFT-based methods for predicting qualitative thermochemistry of large polyaromatics.
abstract: We present a validation of computationally efficient density functional-based methods for the reproduction of relative bond dissociation energies of large polyaromatic hydrocarbons. Through the calculation of intrinsic radical stabilities and the computation of spin densities, the extent of delocalization of the unpaired electron in the benzylic radicals is examined. We focus on the influence of the level of theory choice applied for the geometry optimization and the role of van der Waals corrections on thermochemical properties. The dispersion effects mainly influence the energetics, causing a small upward shift of the bond dissociation energies. The long-range corrected CAM-B3LYP functional does not improve the traditional B3LYP results for the geometry description of the large delocalized radicals, however a non-negligible influence was encountered when applied for the energetics. It is reported that the f polarization functions present in the 6-311+G(3df,2p) basis set lead to an erroneous trend when combined with the B2PLYP functional for the computation of the single point energies.
authors: Center for Molecular Modeling, Ghent University, Technologiepark 903, Zwijnaarde, Belgium. Karen.Hemelsoet@UGent.be
authors: Karen
authors: K
authors: Hemelsoet
authors: Freija
authors: F
authors: De Vleeschouwer
authors: Veronique
authors: V
authors: Van Speybroeck
authors: Frank
authors: F
authors: De Proft
authors: Paul
authors: P
authors: Geerlings
authors: Michel
authors: M
authors: Waroquier