Double-Roaming Dynamics in the H + C₂H₂ → H₂ + C₂H Reaction: Acetylene-Facilitated Roaming and Vinylidene-Facilitated Roaming

Abstract

We report two novel roaming pathways for the H + C 2 H 2 → H 2 + C 2 H reaction by performing extensive quasiclassical trajectory calculations on a new, global, high-level machine learning-based potential energy surface. One corresponds to the acetylene-facilitated roaming pathway, where the H atom turns back from the acetylene + H channel and abstracts another H atom from acetylene. The other is the vinylidenefacilitated roaming, where the H atom turns back from the vinylidene + H channel and abstracts another H from vinylidene. The "double-roaming" pathways account for roughly 95% of the total cross section of the H 2 + C 2 H products at the collision energy of 70 kcal/ mol. These computational results give valuable insights into the significance of the two isomers (acetylene and vinylidene) in chemical reaction dynamics and also the experimental search for roaming dynamics in this bimolecular reaction.

Full-dimensional neural network potential energy surface and dynamics of the CH2OO + H2O reaction

“…41 The FI-NN approach minimizes the size of polynomial and efficiently reduces the evaluation time of the potential energy, in particular for larger molecular systems with more identical atoms. [43][44][45][46] Moreover, FIs are polynomials based on the internuclear distances, which are invariant for translation, rotation, and inversion.…”

Roaming Dynamics in Hydroxymethyl Hydroperoxide Decomposition Revealed by the Full-Dimensional Potential Energy Surface of the CH2OO + H2O Reaction

“…The concept of the roaming mechanism was first introduced in the context of the photodissociation of H 2 CO, motivating a surge of interest in exploring its presence within other systems. These discoveries of roaming pathways have predominantly centered around unimolecular dissociation systems, − although recent evidence has emerged showing roaming in bimolecular reactions as well. − For instance, beyond the complex-forming roaming process, we reported a novel collision-induced roaming in the H + C 2 H 4 → H 2 + C 2 H 3 reaction . Recently, the double-roaming mechanism was first found in the H + C 2 H 2 → H 2 + C 2 H reaction, involving the acetylene-facilitated roaming and vinylidene-facilitated roaming pathways.…”

“…48−52 For instance, beyond the complexforming roaming process, we reported a novel collisioninduced roaming in the H + C 2 H 4 → H 2 + C 2 H 3 reaction. 52 Recently, the double-roaming mechanism was first found in the H + C 2 H 2 → H 2 + C 2 H reaction, 51 involving the acetylenefacilitated roaming and vinylidene-facilitated roaming pathways. Those findings of intricate roaming mechanisms underscore the importance of comprehensive dynamics simulations utilizing accurate, full-dimensional PESs.…”

“…Roaming, an unconventional yet intriguing mechanism, promises to yield unexpected products with final distributions remarkably distinct from those generated by the traditional MEP. − This phenomenon is characterized by the initial frustrated dissociation, giving rise to radical products, followed by the meandering of these nascent radicals. Ultimately, this intricate process leads to intramolecular abstraction and formation of the end products.…”

Accurate fundamental invariant-neural network representation of ab initio potential energy surfaces

“…It is essential to have an accurate global PES to accurately study the dynamics of this reaction. We recently developed a new global full-dimensional PES using FI-NN fitting based on ∼116 000 UCCSD(T)-F12a/aug-cc-pVTZ energies [ 61 ]. These UCCSD(T) energies were all calculated using the Molpro program [ 85 ].…”