On the description of chemical bonding using the electrostatic potential. I. Theoretical introduction and covalent interactions

The interpretation of molecular properties and reactivity has been, in general, primarily based on the electron density distribution with little to no explicit consideration of the nuclei. However, many examples show that the nuclei can have a significant influence on atomic and molecular properties. The electrostatic potential, however, carrying a term describing the influence of the nuclei next to a term describing the effect of the electrons, considers both electrons and nuclei as significant contributors to reactivity. In addition to finding the minimum of the electrostatic potential Vrmin along an interaction axis, we follow here the electrostatic potential along this 1-dimensional axis from nucleus to nucleus of the atoms involved in the interaction and examine its shape. We show that this shape is an identification of the nature of the interaction between the interacting atoms. We see that the steepness of the electrostatic potential along the line of interaction, which is its (magnitude of the) gradient of the potential, can be an indication of interaction strength. We conclude that, as the gradient can take all possible consecutive values, there must be a bonding continuum between the different types of classically formulated bonds/interactions.