This paper represents an attempt to extend the mechanisms of reactions and kinetics of a methane combustion reaction.Three saddle points（SPs） are identified in the reaction CH_4＋ O（~3P） → OH ＋ CH_3 using the co...This paper represents an attempt to extend the mechanisms of reactions and kinetics of a methane combustion reaction.Three saddle points（SPs） are identified in the reaction CH_4＋ O（~3P） → OH ＋ CH_3 using the complete active space selfconsistent field and the multireference configuration interaction methods with a proper active space. Our calculations give a fairly accurate description of the regions around the twin first-order SPs（~3A＇ and ~3A〞） along the direction of O（~3P） attacking a near-collinear H–CH_3. One second-order SP^（2nd）（~3E） between the above twin SPs is the result of the C_（3v） symmetry Jahn–Teller coupling within the branching space. Further kinetic calculations are performed with the canonical unified statistical theory method with the temperature ranging from 298 K to 1000 K. The rate constants are also reported. The present work reveals the reaction mechanism of hydrogen-abstraction by the O（~3P） from methane, and develops a better understanding for the role of SPs. In addition, a comparison of the reactions of O（~3P） with methane through different channels allows a molecule-level discussion of the reactivity and mechanism of the title reaction.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51574016 and 51604018)
文摘This paper represents an attempt to extend the mechanisms of reactions and kinetics of a methane combustion reaction.Three saddle points（SPs） are identified in the reaction CH_4＋ O（~3P） → OH ＋ CH_3 using the complete active space selfconsistent field and the multireference configuration interaction methods with a proper active space. Our calculations give a fairly accurate description of the regions around the twin first-order SPs（~3A＇ and ~3A〞） along the direction of O（~3P） attacking a near-collinear H–CH_3. One second-order SP^（2nd）（~3E） between the above twin SPs is the result of the C_（3v） symmetry Jahn–Teller coupling within the branching space. Further kinetic calculations are performed with the canonical unified statistical theory method with the temperature ranging from 298 K to 1000 K. The rate constants are also reported. The present work reveals the reaction mechanism of hydrogen-abstraction by the O（~3P） from methane, and develops a better understanding for the role of SPs. In addition, a comparison of the reactions of O（~3P） with methane through different channels allows a molecule-level discussion of the reactivity and mechanism of the title reaction.
