Evaluation of transition state properties by density functional theory

We have evaluated the performance of five popular DFT functionals, BH&HLYP, B3PW91, B3P86, B3LYP and BLYP, in characterizing a set of seven 'well known' transition states. We found BH&HLYP performs best in calculating classical barrier heights, with the other functionals systematically underpredicting the barriers. All the functionals examined perform reasonably well in predicting geometries, and the BH&HLYP, B3PW91 and B3P86 functionals have similar performance in predicting vibrational frequencies. In examining the effect of basis set size we found essentially no systematic improvement in performance with increase in basis set size from 6-31G(d) to 6-311G(3df,2p).