Potential-energy surfaces for the Li+HF reaction. MRDCI study of the ground- and lower excited-states for doublet LiFH Original Research Article

Ab initio electronic energy calculations are reported for 570 nuclear configurations of LiFH in Cs symmetry (three dimensional potential energy surface). The lower five doublet spin-state eigenfunctions (three 2A′ and two 2A″) for LiFH have been determined using a multiple reference single and double excitations configuration-interaction (MRDCI) method and an extended triple-zeta-plus-polarization contracted Gaussian basis set. As the Li atom approaches the HF diatomic, it first forms a bent complex (106°) with 28 kJ/mol of stabilization energy before reaching the transition state. The latter, also bent (73°) was located in the exit channel and is predicted to be 24 kJ/mol above the reactants. We argue that laser catalysis of the Li+HF→LiF+H reaction would be possible and irradiation in the 6 000–9 000 cm−1 range is predicted to enhance the reaction.