A theoretical study of Li2H. I. Basis set and computational survey of excited states and possible reaction paths

SCF potential curves for C2v (Li2+H) and C∞v (LiH+Li) symmetries have been calculated for the 26 lowest lying states of Li2H. The curves are estimated to be ≲0.1 eV above the Hartree–Fock–Roothaan limit. Correlated MCSCF/CI curves were computed for the lowest states of 2A1, 2B2, and 2Σ symmetries. All low-lying states of the complex Li2H involve substantial charge transfer. The most stable of these, 2A1, lies ∼20 kcal/mole below the ground state LiH+Li asymptote. The first excited state of the complex, 2B2, is but weakly bound relative to the same asymptote. Electron-jump geometries and vertical spectra were computed for all of these low-lying states. Possible low-energy paths for the reaction Li2+H→LiH+Li were determined, and all involve charge-transfer intermediates.