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Accurate full-dimensional quantum mechanical calculations are reported for the CH4+H→CH3+H2 reaction employing the Jordan–Gilbert potential energy surface. Benchmark results for the thermal rate constant and the cumulative reaction probability are presented and compared to classical transition state theory as well as reduced dimensionality quantum scattering calculations. The importance of quantum effects in this system is highlighted.

Quantum mechanical calculations for the thermal rate constant of the combustion related reaction, CH4 + H → CH3 + H2, are reported. Benchmark full-dimensional results are given and compared to those derived from classical transition state theory as well as to some published reduced dimensionality results. The role played by some of the different degrees of freedom in the reactive process is investigated by comparing additional reduced dimensionality results to the exact ones. This proves valuable for the development of possible strategies to study involved reactive processes.

A quantum dynamics study of a polyatomic combustion reaction accurately considering all its internal degrees of freedom is presented. The thermal rate constants for the O(3P)+CH4(X 1A1)→OH(X 2Π)+CH3(X 2A2″) reaction is calculated and compared to experimental and approximate theoretical results. Good agreement with experiment is found and the reliability of some of the approximate approaches is confirmed.

The full dimensional rate constant reported by Huarte-Larrañaga and Manthe for the H+CH4→H2+CH3 reaction [Huarte-Larrañaga and Manthe, J. Chem. Phys. 113, 5115 (2000)] is corrected by using an accurate vibrational partition function for CH4 instead of the harmonic normal-mode one used by them. The correction is shown to be substantial over the temperature range considered by Huarte-Larrañaga and Manthe.

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Accurate quantum mechanical results for the thermal rate constant of the prototypical six atom reaction, CH4+H→CH3+H2, are reported in this article. Previous k(T) results for temperature values below 500 K are extended up to 1000 K. This is achieved employing a combined iterative diagonalization and statistical sampling approach for the evaluation of the flux correlation function. The accurate reaction rate data obtained for the extended temperature range is used to test several approximations related to the transition state theory. The study especially focuses on the contribution of vibrationally excited states of the activated complex to the thermal rate constant.

Rigorous quantum dynamics calculations of reaction rates and initial state-selected reaction probabilities of polyatomic reactions can be efficiently performed within the quantum transition state concept employing flux correlation functions and wave packet propagation utilizing the multi-configurational time-dependent Hartree approach. Here, analytical formulas and a numerical scheme extending this approach to the calculation of state-to-state reaction probabilities are presented. The formulas derived facilitate the use of three different dividing surfaces: two dividing surfaces located in the product and reactant asymptotic region facilitate full state resolution while a third dividing surface placed in the transition state region can be used to define an additional flux operator. The eigenstates of the corresponding thermal flux operator then correspond to vibrational states of the activated complex. Transforming these states to reactant and product coordinates and propagating them into the respective asymptotic region, the full scattering matrix can be obtained. To illustrate the new approach, test calculations study the D + H 2 (ν, j ) → HD(ν , j ) + H reaction for J = 0.