Theoretical investigation of Li and Be atom complexes with H2O

Abstract

The structures, energetics, and vibrational frequencies of the Li–OH₂ and Be–OH₂ complexes have been examined by ab initio molecular orbital methods including the effects of electron correlation by Mo/ller–Plesset perturbation theory. Previous studies, at the Hartree–Fock level, indicated the existence of only a very weak van der Waals‐type complex between Be and H₂O, while the Li–OH₂ complex was strongly bound (10–11 kcal/mol) at this level. In contrast, we find that, when correlation effects are included, the Be interaction with H₂O is quite similar to that of Li with H₂O. The Be–OH₂ complex is predicted to be nonplanar and significantly bound with a short Be–O distance of 1.736 Å and a dissociation energy of 5.53 kcal/mol. The Li–OH₂ complex at the correlation energy level is nonplanar with a Li–O bond distance of 1.90 Å and a dissociation energy of 13.77 kcal/mol. Calculated shifts in the vibrational frequencies of H₂O in Li–OH₂ at the correlated level are in good agreement with the experimental values, whereas Hartree–Fock level frequency shifts are in disagreement.