Dynamics studies for the multi-well and multi-channel reaction of OH with C₂H₂ on a full-dimensional global potential energy surface

Abstract

The C2H2+OH reaction is an important acetylene oxidation pathway in the combustion process, as well as a typical multi-well and multi-channel reaction. Here, we report an accurate full-dimensional machine learning-based...

Mode-Specific Dynamics Studies for the Multichannel C2H2 + OH Reaction

“…The PES for the ground state of the C 2 H 2 + OH reaction used in this work was fitted using the permutation invariant polynomial-neural network (PIP-NN) method 28 by approximately 475,000 ab initio points calculated at the UCCSD(T)-F12b/cc-pVTZ-F12 level. 13 The topography of the PES including multiple potential wells and barriers is shown in Figure 1. The energies labeled are relative to the reactant asymptote and with zero-point energy (ZPE) correction.…”

“…More details about the PES can be found in our previous work. 13 2.1. Quasi-Classical Trajectory Calculations.…”

“…The C 2 H 2 + OH reaction is known as an important process of acetylene oxidation, 11,12 investigated recently based on a full-dimensional PES. 13 This reaction is a typically multiwell reaction 13−15 Kinetic studies show that at temperatures below 1000 K, the C 2 H 2 + OH reaction mainly produces the C 2 H 2 OH complex, H + OCCH 2 (P3) and CO + CH 3 (P4). 13,15−17 As the temperature increases to higher values, H 2 O + C 2 H (P1) and H + HCCOH (P2) channels become more important, 15,16 with the former dominating at temperatures above 1900 K. 13 It is worth noting that these products are also pivotal in the combustion process.…”

“…13 This reaction is a typically multiwell reaction 13−15 Kinetic studies show that at temperatures below 1000 K, the C 2 H 2 + OH reaction mainly produces the C 2 H 2 OH complex, H + OCCH 2 (P3) and CO + CH 3 (P4). 13,15−17 As the temperature increases to higher values, H 2 O + C 2 H (P1) and H + HCCOH (P2) channels become more important, 15,16 with the former dominating at temperatures above 1900 K. 13 It is worth noting that these products are also pivotal in the combustion process. For example, the hydrogen atom is not only a key species in initiating the important chain branching reaction H + O 2 → O + OH but also has the strongest thermal diffusion effect.…”

“…Extensive research for some other reaction systems has pointed out that the excitation of different reactant modes will give rise to different effects on reactivity, which makes it possible to modulate reactants to control the reactivity. 20−27 In our prior work, we developed the PES for the title reaction and reported the quasi-classical trajectory (QCT) rate coefficients over the temperature range of 298−3000 K. 13 Within the 1000−2000 K temperature range where soot formation is prevalent, the product branching ratios of P1−P4 changes significantly from the 3, 7, 63, and 27% at 1000 K to 36, 25, 31, and 8% at 2000 K. The different initial state distributions of the reactants might significantly change the product branching ratio and product state distribution, which makes this system a good case to study the mode specificity of the multichannel complexforming reaction. A detailed study of mode specificity may also provide some theoretical guidance to regulate the branching ratio of the multichannel C 2 H 2 + OH reaction.…”