Diabatic potential energy surfaces of the HF2 system and dynamics studies of the H + F2 reaction

The diabatic potential energy surfaces (PESs) for the 12A' and 22A' states of HF2 system were constructed using neural network method combined with symmetry-constrained function. The ab initio calculations were performed at the MRCI-F12/aug-cc-pVTZ level of theory to obtain the electronic energies. The features of the diabatic PESs are examined in detail, and the results indicate that the newly constructed diabatic PESs can reasonably describe the nonadiabatic transition processes. To clarify the nonadiabatic effect in the H + F2 reaction, the adiabatic and nonadiabatic dynamics studies were performed using time-dependent wave packet method. The dynamical quantities, including reaction probabilities, integral cross sections and rate constants, were calculated and compared with available theoretical and experimental values. Both our nonadiabatic and adiabatic results show better agreement with experimental data than previous theoretical studies. In low collision energy range, adiabatic values are in good agreement with nonadiabatic ones. However, the difference between adiabatic and nonadiabatic values becomes more pronounced as the collision energy increases.