Solid Solutions Mixed Crystals and Eutectics

Nonstoichiometric systems are often found in mineralogy and metallurgy but more rarely in molecular and network crystals. These solids are characterized by a variable composition that affects structural and physicochemical properties in a predictable manner. In this view, nonstoichiometric systems can contribute to the scope of crystal engineering and material science by enabling the determination of the relationship between structure and properties and the rational design of crystalline solids.Here, solid solutions, mixed crystals, and eutectics are discussed from a crystal engineering perspective. First the terms are introduced with reference to the historical context in which the same were defined, and the thermodynamic elements to understand multicomponent systems are explained. Main synthetic and analytic methods used in the investigation of these materials are described. Finally a review of recent literature is presented with particular attention to pharmaceutical and porous crystals.