Assessment

Abstract

In these Lecture Notes, chemical bonds, their intrinsic energies and the energies required for bond breaking are at the very center of our attention. Rooted in Hartree-Fock theory, our approach ends up with a formalism, reminiscent of that given by Thomas-Fermi theory, featuring the electrostatic potentials at the nuclei. Both for ground-state atoms and molecules at equilibrium in the Born-Oppenheimer approximation, the total (kinetic + potential) energies are expressed as simple functions of these potentials. The latter are obtained from straightforward applications of the Hellmann-Feynman theorem, the nuclear charges being taken as parameters in these energy derivatives. For molecules, considering such an energy derivative for each individual nucleus, we thus introduce the concept of ‘atom in a molecule’—differing, of course, from an isolated ground-state atom—and then, from an appropriate pairing of atomic terms, we achieve an effective bond-by-bond partitioning of a molecule—avec tout ce que cela comporte— carrying a vivid operational mathematical representation of chemical bonds and their intrinsic energies in molecules at equilibrium.