Thermodynamical Principles and the Landau Theory of Phase Transitions
Phase transitions in condensed matter can basically be interpreted within the scope of thermodynamical principles, while for critical regions precise knowledge of transition mechanisms is essential. In most textbooks on thermodynamics , , , phase equilibria in isotropic media are discussed at some length as simple examples, while structural phase transitions in crystals are complex and described only in a sketchy manner , . In nature, there are various types of phase transitions, which Ehrenfest  classified in terms of a derivative of the thermodynamical potential exhibiting a discontinuous change at T c. Among others, the second-order phase transition characterized as a continuous change of the Gibbs potential has attracted many investigations, since the problem is closely related to a fundamental subject of lattice stability. In this chapter, the continuous-phase transition is discussed in the light of thermodynamical principles, but it is significant that critical anomalies and subsequent domain formation in the low-temperature phase cannot be properly elucidated, hence pertaining to an area beyond the limit of classical thermodynamics.
KeywordsPhase Transition Domain Wall Critical Exponent Structural Phase Transition Landau Theory
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