A SAPT Study of the H2O X2 Complexes; X = H, N and F

The interaction energy of the H₂O⋯X₂ complexes, with X = H, N and F has been analyzed by using the SAPT (Symmetry Adapted Perturbation Theory) methodology. The decomposition of the interaction energy into distinct physical components is a unique feature of SAPT which distinguishes this method from the super molecular approach. In SAPT, the interaction energy is expressed as a sum of perturbative corrections, each correction resulting from different physical effect. SAPT results show that the above systems possess quite different features, while the complex with hydrogen is dominated by dispersion, a subtle balance of dispersion and induction is effective in stabilizing the complex H₂O⋯N₂, and induction (due to the strong electro negativity of fluorine) is the leading term in the pre-reactive vdW complex H₂O⋯F₂.