Full-dimensional ab initio potential energy surface and vibrational configuration interaction calculations for vinyl

Area of Science:

• Chemical Physics
• Theoretical Chemistry
• Quantum Chemistry

Background:

• The vinyl radical (C(2)H(3)) is a key intermediate in combustion and atmospheric chemistry.
• Accurate potential energy surfaces (PESs) are crucial for understanding its reactivity and dynamics.
• Previous studies may have lacked full-dimensional, ab initio-based PESs for the doublet vinyl radical.

Purpose of the Study:

• To develop two accurate, permutationally invariant, full-dimensional ab initio-based potential energy surfaces (PESs) for the doublet vinyl radical (C(2)H(3)).
• To characterize the stationary points on these PESs, including minima, saddle points, and dissociation pathways.
• To utilize the developed PESs for vibrational calculations and comparison with experimental data.

Main Methods:

• Ab initio electronic structure calculations using the spin-restricted coupled cluster singles and doubles with perturbative triples (SR-CCSD(T)) method and augmented correlation consistent polarized valence triple zeta (aug-cc-pVTZ) basis sets.
• Least-squares fitting of electronic energies to permutationally invariant polynomials in Morse variables with a many-body expansion.
• Full-dimensional vibrational configuration interaction (VCI) calculations.

Main Results:

• Two PESs, PES/S and PES/D, were generated for the doublet vinyl radical.
• PES/S describes the global minimum, saddle points for H-atom migration, and a methylcarbyne local minimum arising from a Jahn-Teller conical intersection.
• PES/D includes all features of PES/S and additionally describes the dissociation pathway to C(2)H(2)+H fragments.
• Vibrational configuration interaction calculations using PES/S provided vinyl zero-point and fundamental vibrational energies.

Conclusions:

• The developed PESs provide a comprehensive description of the vinyl radical's potential energy landscape.
• The calculated vibrational energies show good agreement with recent experimental results, validating the accuracy of the PESs.
• These PESs are valuable resources for future theoretical studies on vinyl radical dynamics and reactions.