Molecular Surfaces, van der Waals Radii and Electrostatic Potentials in Relation to Noncovalent Interactions

We investigate two questions relating to the use of electrostatic potentials in interpreting and predicting noncovalent interactions. First, is the molecular surface defined by the 0.001 au contour of the electronic density a reasonable one, in terms of its relationship to the van der Waals radii of the component atoms? Second, how does the electrostatic potential vary with distance in different directions from the nuclei of covalently-bonded atoms? We address these questions computationally, at the density functional B3PW91/6-31G(d,p) level.