We also investigate the design principle of internal space for hosting the anionic electron in candidate compounds. In order to assess the influence of internal distance on the identified electrides, we treat the nearest neighbour distance from the off-atom peak in electron density as a variable; the Please do not adjust margins Please do not adjust margins results of which are shown in Figure . The x-axis is the minimum distance we set and the y-axis is the number of candidates containing electron density maxima greater than that distance from the nearest atom. The electride candidates at each distance are shown in the SI Table . The figure shows the perhaps unsurprising trend that, as the cut-off distance is increased, the number of the candidates decrease quite sharply. However, it is interesting to observe that at 2.8 Å cutoff, all five of the known electrides are present in the 9 candidates alongside Sr 3 RuN 3 , Sr 3 OsN 3 , 𝐸𝑢𝐴𝑙 2 𝑆 4 and 𝐵𝑎 3 𝐴𝑙𝑂 4 . In these, Sr 3 RuN 3 and Sr 3 OsN 3 have same prototype structure and consistent formula with the experimentally confirmed electride Sr 3 CrN 3 (previously discussed as the first redox active electride) and 𝐵𝑎 3 𝐴𝑙𝑂 4 which has a similar composition, component elements and acquisition methods to the confirmed electride 𝐶𝑎 12 𝐴𝑙 14 𝑂 32 . Increasing the cutoff further to 2.9 Å results in the three confirmed electrides 𝐶𝑎 2 𝑁, 𝐵𝑎 2 𝑁 , 𝐶𝑎 12 𝐴𝑙 14 𝑂 32 being eliminated among others and leaving the following compounds remaining: Sr2N, Cs3O and EuAl2S4. Sr2N is a previously confirmed electride, Cs3O is a previously predicted electride, but to the knowledge of the authors EuAl2S4 has not yet been considered as an electride.