Theoretical studies on NH₂ + NO₂ reaction: Driven by reaction dynamics

Chemical dynamics simulations have been performed to study the NH₂ + NO₂ reaction on singlet potential energy surface at 298 K. To obtain more accurate potential energy surface, seven methods including MP2, B3LYP, OPBE, BhandH, HCTH407, M06 and M06–2X combined with aug-cc-pVDZ basis set were employed to calculate the properties of stationary points and the results are compared with the higher level CCSD(T) benchmark and the available theoretical and experimental values. The reaction reactivity, product branching ratio, and detailed microscopic reaction mechanisms are uncovered by direct dynamics simulations at the chosen B3LYP/aug-cc-pVDZ level of theory. The branching ratio between product P1 (N₂O + H₂O) : P2 (H₂NO + NO) determined in current study is 0.22 : 0.78, which is in consistent with experimental observations. The study reveals a preference of P2 channel over P1 at 298 K, although the latter channel is more exothermic. This result indicates the dynamical factors govern the competition of two product channels. Three atomic mechanisms were determined and discussed in detail, in which the indirect reaction dominates. Interestingly, these indirect reactions follow the intrinsic reaction coordinate of the potential energy surface.