Reliable approach for prediction of heats of formation of polycyclic saturated hydrocarbons using recently developed density functionals

The efficiency of recently developed ωB97X-D and M06-2X density functionals was investigated for estimating the gas phase and the condensed phase heats of formation of 27 polycyclic saturated hydrocarbon CnHn′ (5 ⩽ n ⩽ 12). The homodesmotic reaction of CnHn′ + m(C2H6) → x(C3H8) + y(C4H10) + z(C5H12) was used where the experimental reference data are available in the literature. The reliability of predicted results through these density functionals were also compared to the corresponding values calculated by B3LYP and MP2 computational approaches. The maximum absolute (MAX), mean absolute (MAE) and root mean squared (RMS) errors are decreased in moving from B3LYP to ωB97X-D and M06-2X. The performance of ωB97X-D and M06-2X methods is also good with respect to MP2. All three M06-2X, ωB97X-D and MP2 methods show excellent linear relationship with the experimental data. The second order perturbation theory does not reduce the MAX, MAE and RMS errors more than that for ωB97X-D and M06-2X methods.