Full-dimensional automated potential energy surface development and dynamics for the OH + C₂H₆ reaction

Area of Science:

• Chemical Kinetics
• Computational Chemistry
• Reaction Dynamics

Background:

• Understanding the OH radical's reactivity is crucial for combustion and atmospheric chemistry.
• Ethane (C2H6) is a fundamental alkane relevant to hydrocarbon oxidation.

Purpose of the Study:

• To develop a high-accuracy, full-dimensional analytical potential energy surface (PES) for the OH + C2H6 reaction.
• To investigate the reaction dynamics and mechanisms using quasi-classical trajectory simulations on the newly developed PES.

Main Methods:

• Utilized the Robosurfer program system for automated PES development, including geometry selection, ab initio calculations (coupled-cluster singles, doubles, and perturbative triples-F12/triple-zeta quality), and fitting.
• Employed permutationally invariant monomial symmetrization for energy fitting.
• Performed quasi-classical trajectory simulations to analyze reaction pathways, cross sections, and product energy distributions.

Main Results:

• Hydrogen abstraction forming H2O + C2H5 is the dominant reaction channel in the 10-50 kcal/mol collision energy range.
• Reaction mechanism shifts from rebound to stripping with increasing collision energy, indicated by opacity functions and scattering distributions.
• OH radical exhibits a preference for side-on attack, while C2H6 acts largely as a spherical molecule.
• Collision energy primarily partitions into product translation, with minimal dependence on collision energy for product internal energy distributions.

Conclusions:

• The developed PES accurately describes the OH + C2H6 reaction dynamics.
• Collision energy significantly influences the reaction mechanism and product scattering.
• Product vibrational distributions show minor deviations from zero-point energy, while rotational distributions are sensitive to collision energy.