Polarizability differences create forces

Finally, dispersion forces act between molecules. They appear due to the displacement of nuclei and the electronic shell appeared for a very short time, which results in the formation of an instant dipole. The interaction of such existing for a short time dipoles creates forces of dispersion interaction London forces). The energy of dispersion interaction between the same biatomic molecules depends on the polarizability of the molecule a and the zero-point frequency of vibrations of atoms Vo- t isp = -2>a hvJAr. Depending on the structure and sizes of the molecule, the contributions of the orientation, induced, and dispersion interactions differ. The example is presented below (the energies are expressed in kJ/mol accepted that e = 1). 

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