Three Types of Polarization

Dipole moment density occurs as a result of very small translational displacements of the electronic cloud with respect to the nucleus, whether in single atoms or in molecules. Displacement of electrons is very fast (picosecond), and the dispersion is in the gigahertz region. Induced dipoles will have the direction of the local E-field and undergo no rotation. 

Molecules may form permanent dipoles (polar molecules), which of course will also be influenced by an externally applied electric field. A polyatomic molecule is nonpolar if it fulfills certain symmetry criteria. Water molecules are asymmetrical and therefore polar. 

In polar materials, rotational movements will be caused by the torque experienced by permanent dipoles in electric fields. 

This is displacement of positive ions with respect to negative ions. To clarify the division between electronic and ionic polarization electronic polarization is the displacement of the electron cloud with respect to the nucleus ionic polarization is the displacement of ions relative to each other. The hydrated sheath around an ion at rest is symmetrical (not really at rest, everything is bumping around at room temperature, we are talking statistically). When current flows, the sheath will lag behind the migrating ion, and the sheath is no longer symmetrical to the ion, cf. the Wien effect (Section 8.4.1). This is local polarization of charges bound to each other. 

A molecule with a net charge 0 will experience a translational force and therefore try to migrate in a homogeneous electric field. A dipole with net charge = 0 will also experience a translational force, but only in an inhomogeneous field. 

---

As shown in Fig. 8, three types of polarization exist during the discharge of porous MnOa. The battery active EMD or CMD (chemical manganese dioxide) is highly porous and the concentration polarization due to the pH change, r (ApH), is very important. Kozawa studied the three types of... 

Figure 8. Three types of polarization of Mn02 (1) J]c (H+ solid), due to proton diffusion in solid (2) rja, due to the solution-solid interface (3) 7/t (ApH), due to a pH change of the electrolyte in the pores.

Figure 18.10 Three types of polarization curves typically manifested by simple Fe and Co porphyrins and cofacial metaUoporphyrins (simulated voltammograms).

The mechanisms that cause polarization depend on the frequency of the applied electric field and the composition of the material. Real permittivity increases as frequency decreases since polarizations accumulate (see Figures 1 and 2). Single-phase materials may experience three types of polarization electronic (r 10-16s), ionic (r 10-13s), and orientational (r =variable). Non-polar materials do not experience orientational polarization and have very... 

Polarization is defined as a type of perturbation, which results in disturbing the equilibrium and producing a dynamic situation. The three types of polarization are concentration polarization, activation polarization, and IR drop. 

In a polar medium, three types of polarization are observed. The first type results from the deformation of the electron coulds in solvent molecules. The frequency of fluctuation of this polarization, v, is given by... 

If vdielectric permittivity in vacuum will then be equal to 80. This is the so-called static permittivity. The permittivity of the vaccum is 0.855x 10 C m. The static dielectric permittivity near the ion or the surface of the charged electrodes, however, will exhibit smaller values. For instance, in the case of water at the electrode surface is assumed to approach 6. When applying the Marcus theory [8] both static and optical permittivities are used in calculations. These parameters therefore are listed in Table 1. In other calculations and correlations of the rate constants of electrode reactions and the dynamic relaxation properties of the solvents, the relaxation time of the solvents is used (Thble 1). 

All three types of polarization interactions—Keesom, Debye, and London—are included in the following formula for the total van der Waals interaction potential between two spherical molecules separated by a distance r ... 

The dielectric constant of a material depends primarily on its polarizability and, hence, strongly depends on density. The three types of polarization that contribute to the dielectric constant are electronic, ionic, and orientational polarizations and are given by the Debye equation ... 

Suppose that our thin-film layer covers cylindrically the pore as shown in Figure 16.6. We are going to consider that three types of polarizations occur obeying... 

HM fiber in particular, which necessitates the use of higher treatment currents, can exhibit three types of polarization which can slow the process down ... 

A number of antibiotics were examined using both FDMS and SIMS (772). The techniques were about equally effective for the easier examples, but for the more polar molecules SIMS was more effective. Thus phosphoramidone (50) containing three types of polar moiety (amino acid, carbohydrate and ionized phosphate) gave no molecular ion in FDMS but a small [M-l-2Na —H] ion in SIMS. In using SIMS for the structural... 

---