Interatomic potentials
Theory of molecular spectra

When two atoms approach each other, the valence electrons of each will be influenced by the attractive potential of the nucleus of the other. The result is a rearrangement of the electron distribution that tends to minimize the total energy of the system made up of the two atoms. The attractive force between the two atoms increases as the internuclear distance R decreases, until R becomes sufficiently small that repulsive forces become predominant. This is due both to the internuclear potential Z_AZBe²/(4πε ₀R) ZAe and ZBe being the respective charge of the two nuclei) and to the Pauli repulsion due to the overlap of nearby electron layers.

Repulsive forces may eventually dominate attractive forces, giving rise to a potential V(R) of the form shown in figure 1...