The theory behind dispersive interactions is complex but it can be stated that the interaction energy, (UD), involved with such forces can be expressed as
| where (ap) | is the polarizability of the molecule, |
| (vo) | is the characteristic frequency of the molecule, |
| (hp) | is Planck's constant, |
| and (l) | is the distance between the molecules. |
The polarizability (a) is the crucial factor that controls the dispersive force acting on the molecule, which, for substances that have no dipoles, is given by
| where (D) | is the dielectric constant of the material |
| and (nv) | is the number of molecules per unit volume. |
