Performance of the correlation consistent composite approach for transition states: A comparison to G3B theory


The correlation consistent composite approach (ccCA) was applied to the prediction of reaction barrier heights (i.e., transition state energy relative to reactants and products) for a standard benchmark set of reactions comprised of both hydrogen transfer reactions and nonhydrogen transfer reactions (i.e., heavy-atom transfer, SN 2, and unimolecular reactions). The ccCA method was compared against G3B for the same set of reactions. Error metrics indicate that ccCA achieves "chemical accuracy" with a mean unsigned error (MUE) of 0.89 kcalmol with respect to the benchmark data for barrier heights; G3B has a mean unsigned error of 1.94 kcalmol. Further, the greater accuracy of ccCA for predicted reaction barriers is compared to other benchmarked literature methods, including density functional (BB1K, MUE=1.16 kcalmol) and wavefunction-based [QCISD(T), MUE=1.10 kcalmol] methods. © 2007 American Institute of Physics.

Publication Title

Journal of Chemical Physics