Theodore Dibble - Impact of tunneling on hydrogen-migration of n-propylperoxy radical

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      Publication Details (including relevant citation   information):

      Physical Chemistry Chemical Physics,   2011, 13, 17969-77.


      The kinetics of three unimolecular reactions of   n-propylperoxy radical were studied by canonical   variational transition state theory and multidimensional small   curvature tunneling (SCT). The reactions studied were 1,5 and 1,4   H-migration, and HO2 elimination. Benchmark   calculations were carried out at the CCSD(T) level in order to   determine which density functional to use for SCT calculations   for each reaction. For 1,5 and 1,4 H-migration, and   HO2 elimination, the M05-2X, B3LYP and B1B95   functionals, respectively, performed closest to the benchmark   when coupled to the 6-311+G(2df,2p) basis set. The SCT tunneling   corrections, Κ(T), computed here were much larger than   those calculated from the Wigner or zero-curvature tunneling   treatments at low temperature, but the asymmetric Eckart method   works surprisingly well in these three reactions. Comparison of   energy-dependent transmission coefficients, Γ(E),   indicates that not only the magnitude, but also the sign, of the   error in the Eckart approximation is a function of energy;   therefore, the error introduced by using the Eckart approach   depends strongly on the steady state energy distribution. These   results may provide guidance for future studies of tunneling   effects in reactions of other peroxy radicals.

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