Shared-shell interatomic interactions

The opposite extreme to a shared interaction occurs when two closed-shell systems interact, as found in ionic, hydrogen-bonded, van der Waals, and repulsive interactions. In such closed-shell interactions, the requirement of the Pauli exclusion principle leads to the removal of electron density from the region of contact, the interatomic surface. All of the curvatures of Pb are relatively small in magnitude but the positive curvature of Pb along the bond path is dominant and V pb > 0. Since the electron density contracts away from the surface, the interaction is characterized by a relatively low value of pb and the electron density is concentrated. separately in each of... 

Fig. 7.19. Contour maps of the Laplacian of p for second- and third-row diatomic hydrides. The intersection of the interatomic surface with the plane of the diagram is also shown. These maps illustrate the transition from closed-shell to shared atomic interactions.

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