Ab initio potential energy surface and excited vibrational states for the electronic ground state of Li2H

A 285-point multi-reference configuration-interaction involving single and double excitations (MRSDCI) potential energy surface for the electronic ground state of Li2H is determined by using 6-311G (2df, 2pd) basis set. A Simons-Parr-Finlan polynomial expansion is used to fit the discrete surface with a chi(2) of 4.64 X 10(-6). The equilibrium geometry occurs at R-e = 0.172 nm and angle LiHLi = 94.10(.). The dissociation energy for reaction Li2H((2)A') --> Li-2((1) Sigma(g)) + H(S-2) is 243.910 kJ/mol, and that for reaction Li2H((2)A') --> HLi((1) Sigma) + Li(S-2) is 106.445 kJ/mol. The inversion barrier height is 50.388 kJ/mol. The vibrational energy levels are calculated using the discrete variable representation (DVR) method.