Accurate Determination of Barrier Height and Kinetics for the F + H 2O → HF + OH Reaction


The reaction energy and barrier height of the title reaction are investigated using two high-level ab initio protocols, namely Focal Point Analysis (FPA) and modified High Accuracy Extrapolated Ab Initio Thermochemistry (HEAT) methods. It is concluded from these calculations that despite some multireference character, dynamic electron correlation plays a dominant role near the reaction barrier. Thus, the coupled-cluster method with higher excitations than singles and doubles gives a better description than the multireference configuration interaction method for the barrier height. The FPA and HEAT classical barrier heights, including the spin-orbit and other corrections, are 1.919 and 2.007 kcal/mol, respectively. The rate constants and H/D kinetic isotope effect for the title reaction are determined by semiclassical transition-state theory based on the anharmonic potential energy surface near the saddle point, and the agreement with experiment is excellent. The rate constants are also computed using a quasi-classical trajectory method on a global potential energy surface scaled to the FPA barrier height and a similar level of agreement with experimental data is obtained.



Keywords and Phrases

Ab initio thermochemistries; Anharmonic potential energy; Coupled-cluster methods; Global potential energy surfaces; Kinetic isotope effects; Multireference configuration interaction methods; Quasi-classical trajectory method; Transition state theories; Isotopes; Potential energy surfaces; Quantum chemistry; Rate constants; Calculations

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Article - Journal

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© 2013, American Chemical Society (ACS), All rights reserved.

Publication Date

01 Sep 2013