Engineering Crystal Properties through Solid Solutions

The control of structures and properties in crystalline materials has many returns that justify the increasing efforts in this direction. Traditionally, crystal engineering focused on the rational design of single component molecular crystals or supramolecular compounds (i.e., cocrystals). More recently, reports on crystalline solid solutions have become common in crystal engineering research. Crystalline solid solutions are characterized by a structural disorder that enables the variation of stoichiometry in continuum. Often such variation corresponds to a variation of structural and physicochemical properties, and offers an opportunity for the materials' fine-tuning. In some cases, though, new and unexpected properties emerge. As illustrated here, both behaviors make solid solutions particularly relevant to the scope of crystal engineering.