Three types of polarization mechanisms

There are several mechanisms of dielectric polarization, each being directly dependent on the molecules structure. 

Let us distinguish a deformation and an orientation polarization. In the first case the molecule deformation takes place when imposing it in the external field. Deformation can touch both the single atom and the whole molecule. We shall consider each of these mechanisms separately. 

Relates to the deformation type of polarization and appears as a result of the displacement of an atomic electron shell relative to the nucleus which, accordingly, leads to an induced dipole moment. Certainly, such a polarization mechanism takes place in all systans containing atoms, i.e., in all dielectrics however, in a pure state it can be seen in the case of nonpolar homo-atomic molecules and atoms. 

Let us estimate the value of electronic polarization. As an example, take a simplified model of an atom. Assume that the electron charge Ze is uniformly distributed around the nucleus in a sphere of radius R, i.e., with constant electron density p=Q/((4/3)jt/ )=Z e /((4/3) tR ). In the absence of an external electric field, the nucleus is in the center of a spherically symmetric electronic cloud, the centers of positive and negative charges coincide the atom does not possess a dipole moment. We can impose an origin with negative charge center. 

It can be seen that the atomic electron s ability to be polarized is proportional to its volume. Although the result has been obtained at a certain level of simplification, it is qualitatively correct in describing a real picture of electron polarization. It can be seen from Table 4.2 that a cube of atomic radius increase and an electronic polarizability change in parallel. 

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