Density-functional description of electrides

Electrides are a unique class of ionic solids in which the anions are stoichiometrically replaced by electrons localised within the crystal voids. There are only nine electrides with known crystal structures and their study represents a challenge for theory. A systematic investigation of their electronic structure is conducted using semilocal density-functional theory (DFT) in this article. The band structure is calculated for each electride and a range of techniques including plots of the valence densities, procrystal densities, non-covalent interaction isosurfaces, and Bader's quantum-chemical topology are applied. All of these methods provide consistent results, confirming the presence of localised interstitial electrons and demonstrating that these crystals display a characteristic electronic structure.