Hybrid density functional theory with a specific reaction parameter: hydrogen abstraction reaction of difluoromethane by the hydroxyl radical

Abstract

Accurate potential energy surfaces for the OH + CH2F2 --> H2O + CHF2 reaction are constructed using hybrid and hybrid meta density functional theory methods (mPW1PW91, B1B95, and mPW1B95) with specific reaction parameters in conjunction with the 6-31 + G(d,p) basis set. The accuracy of a surface is examined by comparing the calculated rate constants with the experimental ones. The rate constants are calculated over the temperature range 200-1,500 K using variational transition state theory with multidimensional tunneling contributions. The hybrid density functional theory methods with specific-reaction-parameter Hartree-Fock exchange contributions (39.2-41.0% for mPW1PW91, 41.0-42.2% for B1B95, and 44.9-46.3% for mPW1B95, respectively) provide accurate rate constants over an extended temperature range. The classical barrier height for the hydrogen abstraction reaction on these potential energy surfaces is determined to be 5.0-5.3 kcal mol(-1), and the best estimate value is 5.14 kcal mol(-1).