ABSTRACT
The first hint that there are non-covalent interactions between uncharged atoms and molecules came from the observations of van der Waals (1873, 1881). These interactions came to be known as "van der Waals forces." The interactions responsible for these became clear with the work of Keesom (1915, 1920, 1921), Debye (1920, 1921) and London (1930) as, respectively, interactions between two permanent dipoles (orientation forces), a permanent dipole and an induced dipole (induction forces) and a fluctuating dipole and an induced dipole (dispersion forces). While these three kinds of interaction have different origins, the interaction energies for all three vary as the inverse of the distance raised to the sixth power:
where [JL is the dipole moment, k is the Boltzmann constant, T is the absolute temperature, a is the polarizability, i is the interatomic distance, v is the main dispersion frequency and h is Planck's constant.
