Assessment of hybrid, meta-hybrid-GGA, and long-range corrected density functionals for the estimation of enthalpies of formation, barrier heights, and ionisation potentials of selected C1–C5 oxygenates

Abstract

The enthalpies of formation for some selected oxygenates have been calculated by the atomisation energy approach using B3LYP, BHandHLYP, MPW3LYP, MPW1K, MPWB1K, BB1K, MPW1B95, BMK, and long-range corrected (LC-ωPBE, LC-BOP, LCgau-BOP, LC-BOP12, LCgau-B97) density functionals, as well as the composite CBS-QB3 method. Compared with experiment, BMK, LC-ωPBE, LCgau-BOP, LC-BOP12, LCgau-B97, MPW195, MPW3LYP functionals and CBS-QB3 give root mean square errors (RMSE) in enthalpies of formation no greater than 4 kcal/mol, whilst MPW1K and BHandHLYP show much worse performance (RMSE of 20–40 kcal/mol). The B3LYP, MPWB1K, and BB1K results fall between the two extremes. Energy barriers for the dominant paths in the unimolecular decomposition of simple esters (HCO2CH3, C2H5CO2C2H5), C1–C3 acids, and 1-butanol are reproduced well by CBS-QB3, BMK, BB1K, LCgau-B97, and PW1B95 (RMSE = 1–2 kcal/mol), while other LC methods (LC-ωPBE, LC-BOP, LCgau-BOP, and LC-BOP12) show a deviation of up to 4 kcal/mol. For the ionisation potentials, calculated from Koopman's theorem, all of the investigated LC-methods give good results compared with other density functional theory functionals with a maximum deviation of 0.4 eV, except for LCgau-B97, which has an RMSE of 0.7 eV.