Performance of the correlation-consistent composite approach for sulfur species

The performance of the correlation-consistent composite approach (ccCA) model chemistry has been examined for a test set of sulfur-containing molecules which includes enthalpies of formation, bond dissociation enthalpies (BDEs), and isomerization energies. The ccCA method was compared with other model chemistries (G3, G3B3) and, overall, was found to be more accurate than both G3 and G3B3 for sulfur-containing species, and at a moderate increase in computational cost. The ccCA model chemistry resulted in a mean absolute deviation (MAD) of 3.6 kJ/mol for the enthalpy of formation test set as compared with 8.3 and 9.6 kJ/mol for G3 and G3B3, respectively. The 95% confidence interval in the enthalpies of formation, which corresponds to two times the root mean square of the deviation from experiment, for the ccCA model chemistry is±10.3 kJ/mol as compared with±23.2 and±27.5 kJ/mol for the G3 and G3B3 methods. For the BDEs, the MAD for ccCA is 2.6 kJ/mol as compared with 4.4 and 4.3 kJ/mol for G3 and G3B3, res...