Calculations of the active mode and energetic barrier to electron attachment to CF3 and comparison with kinetic modeling of experimental results

Abstract

To provide a deeper understanding of the kinetics of electron attachment to CF₃, the six-dimensional potential energy surfaces of both CF₃ and CF₃⁻ were developed by fitting ∼3000 ab initio points per surface at the AE-CCSD(T)-F12a/AVTZ level using the permutation invariant polynomial-neural network (PIP-NN) approach. The fitted potential energy surfaces for CF₃ and CF₃⁻ had root mean square fitting errors relative to the ab initio calculations of 1.2 and 1.8 cm⁻¹, respectively. The main active mode for the crossing between the two potential energy surfaces was identified as the umbrella bending mode of CF₃ in C_3v symmetry. The lowest energy crossing point is located at R_CF = 1.306 Å and θ_FCF = 113.6° with the energy of 0.051 eV above the minimum of the CF₃ electronic surface. This value is only slightly larger than the experimental data 0.026 ± 0.01 eV determined by kinetic modeling of electron attachment to CF₃. The small discrepancy between the theoretical and experimentally measured values is analyzed.