Accurate ab initio-based DMBE potential energy surface for HLi2(X2A′) via scaling of the external correlation

A globally accurate potential energy surface is reported for the electronic ground-state HLi2 by fitting ab initio energies to double many-body expansion formalism. The total 3726 ab initio energies used to map the HLi2 potential energy surface are calculated using the multi-reference configuration interaction method, with their dynamical correlation being semiempirically corrected by the double many-body expansion-scaled external correlation method. The current potential energy surface generates an excellent fit of the ab initio energies, showing a small root-mean squared derivation of 0.636 kcal mol(-1). The topographical features of the HLi2 potential energy surface are examined in detail, which concludes that the H + Li-2(X-1 Sigma(g)) -> Li + LiH(X (1) Sigma) reaction is essentially barrierless and the exothermicity is calculated to be 33.668 kcal mol(-1), thus corroborates the available experimental and theoretical results.