Dielectric crystal

We shall call the frequency at which t = —2em and t" — 0 the Frohlich frequency coF the corresponding normal mode—the mode of uniform polarization—is sometimes called the Frohlich mode. In his excellent book on dielectrics, Frohlich (1949) obtained an expression for the frequency of polarization oscillation due to lattice vibrations in small dielectric crystals. His expression, based on a one-oscillator Lorentz model, is similar to (12.20). The frequency that Frohlich derived occurs where t = —2tm. Although he did not explicitly point out this condition, the frequency at which (12.6) is satisfied has generally become known as the Frohlich frequency. The oscillation mode associated with it, which is in fact the lowest-order surface mode, has likewise become known as the Frohlich mode. Whether or not Frohlich s name should be attached to these quantities could be debated we shall not do so, however. It is sufficient for us to have convenient labels without worrying about completely justifying them. 

Typical values of the second-order nonlinear coefficient d for dielectric crystals, semiconductors, and organic materials used in photonics applications lie in the range d = 10 24 to 10 - (mks units, As/V2). Typical values of the third-order nonlinear coefficient x(3> for glasses, crystals, semiconductors, semiconductor-doped glasses, and organic materials of interest in photonics are x -3 = 10 34 to 10 29 (mks units). 

In the simplest cases, the optical anisotropy of polymer systems is studied under the conditions of simple elongation, when the elongation velocity gradient i/ii is given. The system investigated then becomes, generally speaking, a triaxial dielectric crystal with components of the relative permittivity tensor... 

Barker AS, Loudon R. Response functions in the theory of Raman scattering by vibrational and polariton modes in dielectric crystals. Rev Modern Phys 1972 44 18. 

The more traditional approach to treat the problem outlined by Eq. [13] goes back to the theory of polarons in dielectric crystals. It employs the two-step procedure corresponding to two traces in Eq. [13] first, the trace over the electronic subsystem is taken with the subsequent restricted trace over the nuclear coordinates. This approach, basic to the MH theory of ET, turns out to be very convenient for a general description of several quantum dynamical problems in condensed phases. It is currently widely used in steady-... 

Pockels, F. Ueber die Aenderungen des optischen Verhaltens und die elastischen Deformationen dielektrischer Krystalle im elektrischen Felde. [Concerning the changes in the optical behavior and the elastic deformations of dielectric crystals in electric fields.] Neues Jahrb. Mineral. 7, 201-231 (1891). 

Assume that a dielectric crystal has one electron in the conduction band with effective mass me, and one hole in the valence band with effective mass m/>. If we assume that the interaction between the electron and the hole is given by the... 

Landolt-Bomstein Numerical Data and Functional Relationships in Science and Technology, III/30A, High Frequency Properties of Dielectric Crystals. Piezooptic and Electrooptic Constants, Springer-Verlag, Berlin, 1996. 

Finally, it is worth mentioning that a phenomenon analogous to the difference between the normal and giant flexoelectricity of calamitic and bent-core nematics, respectively, exists in crystals, ceramics and polymers too. The flexoelectric response (defined in Eq. (3.1)) of perovskite-type ferroelectrics, " of relaxor ferroelectric ceramics and polyvinylidene fluoride (PVDF) films are four orders of magnitude larger than the flexoelectricity of dielectric crystals. In those sohd ferroelectric materials the polarization induced by flexing is evidently of piezoelectric origin. 

Joubert M-E, Kazanskii SA, Guyot Y, Gacon J-C, Pedrini C (2004) Microwave study of photocrardnctivily induced by laser pulses in rare-earth-doped dielectric crystals. Phys Rev B 69 165217-1-165217-13... 

NMR parameters of diamagnetic ligands in some dielectric crystals of the Van VIeck paramagnets at liquid... 

EPR parameters of the impurity lanthanide ions with an effective spin 5= j in some dielectric crystals at liquid... 

A large amount of the information in this section is taken from the compilations of low- and high-frequency properties of dielectric crystals in Landolt-Bdmstein, Group m, Vols. 29 and 30, especially Vol. 30b. Since 1992-1993, the date of publication of the first of these volumes, a large amount of new data on the physical properties of dielectrics has appeared in the literature. In particular, various linear and nonlinear optical properties of new crystals in the borate family (BBO, LBO, CBO, and CLBO) and of new organic crystals (DLAP, MNMA,... 

Landolt-Bomstein Tables, Neue Serie Vol. III/29a (Editor D.F. Nelson Springer Verlag. Every AG, McCurdy AK (1992) Low Frequency Properties of Dielectric Crystals. Second and Higher Order Elastic Constants. 

Piezoelectric The generation of electricity or of electric polarity in dielectric crystals subjected to mechanical stress and, conversely, voltage. 

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