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.