Quantifying Electron Delocalization in Electrides

Electrides are ionic solids whose anions are electrons confined to crystal voids. We show that our electron delocalization range function EDR­(r⃗;d), which quantifies the extent to which an electron at point r⃗ in a calculated wave function delocalizes over distance d, provides useful insights into electrides. The EDR quantifies the characteristic delocalization length of electride electrons and provides a chemically intuitive real-space picture of the electrons’ distribution. It also gives a potential diagnostic for whether a given formula unit will form a solid electride at ambient pressure, quantifies the effects of electron–electron correlation on confined electrons’ interactions, and highlights analogies between covalent bonding and the interaction of interstitial quasi-atoms in high-pressure electrides. These results motivate adding the EDR to the toolbox of theoretical methods applied to electrides.