The principle of “derivative structures” in solid-state chemistry, with examples relevant to electronic materials. (Top) The familiar salt and diamond structures (the latter describing silicon) are themselves derived from the simpler face-centered cubic (fcc) structure. (Middle) The III-V crystal structure of derives from by placing different atoms in the fcc and tetrahedral positions, and the structure (describing several small-band-gap thermoelectrics) derives from by filling half of the tetrahedral voids. (Bottom) The structure of semiconductors used in photovoltaic cells is derived from by replacing with an ordered arrangement of and and the structure of (important for half metallic ferromagnets and superconductors) is derived from the structure by filling the remainder of the tetrahedral voids. Finally, (Jungwirth et al.) can be derived from either or . At every step in the derivative pathway, the added chemical degrees of freedom offer more means to tune the electronic properties.