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Theoretical investigations of the ferroelectric transitionLebedev Physical Institute, Russian Academy of Sciences, Leninsky prosp. 53, Moscow, 119991, Russian Federation The paper presents a historical review of theoretical concepts regarding the nature of the ferroelectric transition in crystals with a perovskite structure. We discuss Ginzburg’s phenomenological theory, including the idea of the soft phonon mode as a reason for the ferroelectric transition. The role played by the dipole — dipole interaction in softening the optical phonon mode is considered in the framework of the theory of lattice dynamics. The experimental data and theoretical results are presented that prove that the ferroelectric transition in perovskite crystals is due to the soft mode and is a displacement-type transition.
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