The properties of solids: 'If you want to understand function, study structure'

The importance of the structure-function relationship in molecular biology was confirmed dramatically by the recent award of the 2024 Nobel Prize in Chemistry 'for computational protein design' and 'for protein structure prediction'. The relationship is also important in chemistry and condensed matter physics, and we survey here structural concepts that have been developed over the past century, particularly in chemistry. As an example we take structural phase transitions in phase-change materials (PCM), which can be switched rapidly and reversibly between amorphous and crystalline states. Alloys of Ge, Sb, and Te are the materials of choice for PCM optical memory; they satisfy practical demands of stability and rapid crystallization, which results in metastable, rock salt structures, not the most stable (layered) crystalline forms.