Applications of Diatomics-in-Molecules Theory. I. Prediction of Stable LiH2 and Li2H Molecules

The semiempirical diatomics-in-molecules approach developed by Ellison is applied to the molecules LiH2 and Li2H, both unobserved experimentally. For LiH2, an isosceles triangular A12 state with the diatomic component H2 at its equilibrium internuclear distance is predicted most stable, bound by 13.5 kcal/mole with respect to Li+H2(1Σg+). A linear symmetrical Σu+2 state of Li2H is stable by 19.6 kcal/mole with respect to Li+LiH(1Σ+). Ionization energies, characteristics of potential surfaces, and fundamental vibrational frequencies are predicted for both molecules.