ELECTRON DENSITY ANALYSIS OF WEAK VAN DER WAALS COMPLEXES

The nature of weak van der Waals interactions in different complexes of some atmospheric molecules such as CO 2, N 2 O , and N 2 was examined. Ab initio calculation was carried out at MP2 level of theory using Dunning's aug-cc-pVTZ basis set. Bader's theory of atoms in molecules (AIM) was employed to analyze electron density and to characterize the nature and properties of van der Waals interactions. A set of criteria, having been proposed in the context of AIM theory, was examined for these complexes. In spite of the parameter kinetics energy, per electron density is expected to be greater than unity for closed-shell interactions; we obtained values less than unity for many of these polyatomic systems. A set of limitations has also been outlined for the values of two AIM quantities: total energy density, H(r), and Laplacian of electron density, ∇2ρ, which correspond to different bond natures.