Some Observations Concerning Electronic Densities, Electrostatic Potentials and Chemical Potentials

The hypothesis that the electronic density distribution in a molecule is qualitatively similar to the nuclear potential is shown . to be in error in at least two cases-oxirane and cubane-although it does hold true in a' number of other systems. Its emphasis upon the dominant role played by electrostatic internctions with the nuclei is consistent with some approximate molecular energy formulas. However, taking the nuclear potential as an approximation to the electronic density misses the small effects that correspond to the formation of chemical bonds. It is suggested that the electronic density difference function should provide a rough picture of the local variations in the chemical potential that occur as atoms combine to form a molecule. Finally, the common practice of representing the energy and electronegativity of an interacting atom as functions only of the number of electrons associated with the atom is shown to be ina'dequate; some account should be taken of the changing internuclear separations.