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 calc ulating classical barrier heights, with the other functionals systemat ically underpredicting the barriers. All the functionals examined perf orm reasonably well in predicting geometries, and the BH&HLYP, B3PW91 and B3P86 functionals have similar performance in predicting vibration al frequencies. In examining the effect of basis set size we found ess entially no systematic improvement in performance with increase in bas is set size from 6-31G(d) to 6-311G(3df,2p).