Low-lying states of Li3H: Is there an ion-pair minimum?

Abstract The 1 1 A′, 1 1 A″, 1 3 A′, and 1 3 A″ states of Li 3 H have been investigated at the MCSCF/SOCI level. The global minimum is a planar conformation of 1 A′ symmetry. A local minimum on the same potential surface at a C 3v pyramidal geometry, of mixed ion-pair and covalent character, is found at a relative energy of 20.30 kcal/mol. The barrier height for isomerization is predicted to be 1.3 kcal/mol. The correlation diagram linking states of Li 3 H to those of Li 3 + H, LiH + Li 2 and Li 2 H + Li is presented.