Introduction 453
1. The Dynamic Approach to the Problem of Ferroelectricity 454
1.1. Lattice Dynamics and Stability of Non-piezoelectric Crystals 455
a) General Vibration Equations and the Condition of Structural Stability 455
b) Dielectric Properties of Crystals and Their Relation to the Characteristic Frequencies 458
c) The Physical Mechanism of the Ferroelectric Transition in Cubic Crystals 458
1.2. Application of the Theory to Crystals Having Piezoelectric Properties 451
2. The Role of Anharmonic Effects and Fluctuations and Their Manifestation in Raman Spectra 452
3. Types of Normal Vibrations of Perovskite-type Crystal Structures 463
4. Features of the Experimental Study of the Dynamics of Ferroelectric Crystals 466
4.1. Methods of Infrared Spectroscopy and Raman Scattering 466
4.2. Methods Based on Inelastic Scattering of Slow Neutrons 467
5. Results of Experimental Study of Crystal Lattice Dynamics of Ferroelectric Substances 469
5.1. Infrared Spectra 469
5.2. Raman Spectra 475
5.3. Slow-neutron Inelastic-scattering Spectra 477
5.4. On the Possibility of Studying the Dynamics of Ferroelectric Substances by Using the Mossbauer Effect 481
Conclusion 481
Bibliography 482