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

Abstract

SCF potential curves for C_2v (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.