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

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 C3v symmetry. The lowest energy crossing point is located at RCF = 1.306 Å and θFCF = 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.