Quantum Dynamics of the CH₄ + H → CH₃ + H₂ Reaction:  Full-Dimensional and Reduced Dimensionality Rate Constant Calculations

Abstract

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.

State-to-state reaction probabilities within the quantum transition state framework

“…Accurate full-dimensional quantum dynamics calculations for six atom reactions have up to now only been presented for cumulative reaction probabilities and thermal rate constants [14][15][16][17][18][19][20][21][22][23] or initial state-selected reaction probabilities 24,25 and studied the H + CH 4 → H 2 + CH 3 , [14][15][16][17][18][19][22][23][24][25] [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] and propagated wave packets representing vibrational states of the activated complex which have been a) Electronic mail: rwelsch@uni-bielefeld.de. b) Electronic mail: uwe.manthe@uni-bielefeld.…”

Accurate calculations of reaction rates: predictive theory based on a rigorous quantum transition state concept

“…Based to the combination of MCTDH wave packet propagation and reaction rate calculations via flux correlation functions, larger reactive systems could be investigated in the early 2000s: the first converged full-dimensional quantum dynamics calculation for a six atom reaction studied N (E) and k(T ) for H+CH 4 → H 2 +CH 3 [5,[68][69][70]. Slightly later the reaction O + CH 4 → OH + CH 3 [71] was investigated on the same level of theory.…”

Communications: A rigorous transition state based approach to state-specific reaction dynamics: Full-dimensional calculations for H+CH4→H2+CH3

“…Rigorous full-dimensional quantum dynamics calculations for X +CH 4 reactions have been restricted to the calculation of thermal rate constants and cumulative reaction probabilities for J =0. [4][5][6][7][8][9][10][11][12] Quantum mechanical studies of state-resolved observables have been restricted to reduced-dimensional calculations. The most elaborate studies could include six to seven degrees of freedom explicitly.…”

“…This reaction has emerged as the prototypical benchmark example of a X +CH 4 reaction studied in theoretical research. [4][5][6]8,9,[13][14][15][17][18][19][20][21][22][23][24][25] Most of this research has been based on the Jordan-Gilbert potential energy surface ͑JG PES͒. 26 To allow comparison with previous theoretical work, the JG PES is used also in the present work despite the fact that meanwhile a more accurate global 25 PES has become available.…”