Accurate Potential Energy Surfaces For The First Two Lowest Electronic States Of The Li?2p?+H₂Reaction

Two new global potential energy surfaces?PESs?are obtained for the ground?1²A'?and the first excited electronic states?2²A'?of the LiH₂ system based on high level energies,which play an important role in the astrophysic-related Li+H₂reaction.The ab initio energy points are calculated using the multi-reference configuration interaction method with aug-cc-pV5Z basis set and the cubic spline interpolation are applied in the fitting process.At each state,83930 molecular configurations are selected.The equilibrium distances and dissociation energies for H₂?X¹?_g⁺?and LiH?X¹?⁺?are obtained from our accurate PESs,which are in good agreement with the previous experimental data.The accurate conical intersection?CI?is also studied in this work with three different basis sets.The energy of the conical intersection is slightly higher?nearly0.12 eV?than that of the perpendicular intermediate on the first excited state.Therefore we established two global diabatic potential energy surfaces which are related to the ground and the first excited electronic state of the Li?2p?+H₂ reaction.And the diabatic potential energies are obtained by using the diabatization scheme which is based on transition dipole moment operators.And the transition of the Li?2p?+H₂?X¹?_g⁺??H+LiH?X¹?⁺?reaction occurs in the vicinity of interaction region.Furthermore,we find the cross points of LiH₂ system are nearly on the same line for each angle.By analyzing the potential energy surfaces in this work,the insertion mechanism in bent near-C_2vv collision geometry is favored.The Li?2p?-H₂ collision is initially along the first excited 2²A'potential energy surface in the entrance channel and then transits to the ground 1²A'potential energy surface,finally the products are formed.In other word,the most possible reaction pathway for the title reaction is Li?2p?+H₂?LiH₂?2²A'?(C_2v)?CI?LiH₂?1²A'?(C_2v)?LiH---H?LiH?X¹?⁺?+H.So the conical intersection and the intermediate?2²A'?of first excited electronic state may play a vital role in the title reaction.