Global Diabatic Potential Energy Surfaces of the CH 2 ( 1 A ′ ) System and Dynamics Studies for the C( 1 D ) + D 2 ( v = 0, j = 0) Reaction

The diabatic potential energy surfaces (PESs) for the 1 1 A ′ and 2 1 A ′ states of CH 2 system were constructed using a neural network method combined with symmetry‐constrained function sin( α ). In ab initio calculations, the aug‐cc‐pVTZ basis set is adopted for both H and C atoms, and MRCI‐F12 method is used to compute the energies. Through comparison with ab initio energies and by examining the V 12 symmetry, the PES smoothness, and the minimum‐energy paths of V 11 and V 22 at different angles, we find that the diabatic matrix yields a smooth, symmetry‐adapted representation that accurately reproduces the adiabatic energies. To assess the nonadiabatic effects, we perform adiabatic and nonadiabatic calculations on the new PESs, presenting reaction probabilities, integral cross sections, and rate constants, and comparing them with previous theory and experiment. The results show that nonadiabatic values are slightly larger at low energies, while adiabatic values become larger at higher energies. Overall, the nonadiabatic results are in better agreement with the experimental trend than the adiabatic ones, confirming that nonadiabatic effects within the A ′ manifold are significant and must be included in quantitative dynamics studies. However, the absolute values of our calculated rate constants are lower than the most recent experimental measurements of Hickson et al., indicating that contributions from the 1 1 A ″ state are essential for a complete description of the total reaction rate.