4 Pure component phasechanges: Solid and solid

Abstract

Research in solid–solid phase transitions, also called structural phase transformations, has been active, resulting in well-developed theory and advanced experimental methods. This chapter discusses the fundamentals of the discipline and explains the latest literature of the subject. As the name implies, solid–solid phase transitions are associated with changes in the structure of solids. Solid phase transformations may occur in two different ways. One takes place when the bonds holding together atomic or molecular units break completely to form a new structure, totally unrelated to the initial one. Such transitions are called reconstructive. Second type of transformation occurs when a regular lattice change, without breaking the links of the network, remains closely related to the original. There is, also, another type of nonreconstructive structural phase transitions, involving an order parameter, linked to electron–lattice interactions, known as “electronic phase transformations.” All the three categories are idealizations of real transitions that usually have a “mixed” character and involve elements of more than one type.