data_c2h2cl.rar

The conventional understanding of bimolecular reactions, which either proceed directly via well-defined transition states or pass through potential energy wells, is well-established. However, increasing attention and interest have been drawn to nontraditional reaction pathways, such as roaming mechanisms. Here, full-dimensional dynamics simulations using a highly accurate machine learning-basedpotential energy surface reveal that the Cl + C₂H₂ →C₂H + HCl reaction predominantly follows two novel roaming mechanisms—chlorine roaming (Cl-roaming) and hydrogen roaming (H-roaming)—rather than the expected direct abstraction via the traditional transition state. In the Cl-roaming pathway, a transient C₂H₂Cl adduct forms, followed by the partial dissociation of the chlorine atom, which roams around the acetylene molecule and abstracts a hydrogen atom to form HCl. This mechanism efficiently transfers collision energy into vibrational excitation, facilitating self-abstraction. In the H-roaming pathway, a partially detached hydrogen atom migrates around the C₂HCl intermediate and abstracts the chlorine atom. The roaming pathways account for nearly 100% of the total yield, exhibiting distinct energy and scattering angle partitioning patterns compared to direct abstraction.These findings challenge the traditional view of the bimolecular reaction with conventionaltransition states, emphasizing the importance of considering nontraditional pathways in reaction dynamics studies for accurate rate constant predictions and mechanistic insights.