Electron-Deficient-Type Electride Ca₅Pb₃: Extension of Electride Chemical Space

Abstract

Electrides have been identified so far by two major routes: one is conversion of elemental metals and stoichiometric compounds by high pressure; the other is to search for electron-rich compounds, and this approach is more general. In contrast, few electron-deficient structures in existing databases have been revealed as potential electride candidates. In this work, we found an electron-deficient compound Ca5Pb3 could be transformed into electrides upon applying external pressure or strain along the c-axis, which induces the electron immigration from Pb to interstitial sites. Furthermore, the electron doping via Hf substitution of Ca atoms for Ca5Pb3 was found to be capable of tuning the interstitial electron density under ambient pressure, resulting in a new stable ternary electride Ca3Hf2Pb3, Hf-substituted Ca5Pb3. The electron-deficient electride discovered here is of novel type and can largely expand the research scope of electrides. Considering a recently reported neutral electride Na3N and the present finding, it is now clarified that electrides can be identified irrespective of stoichiometry (electron-rich, -neutral, or -poor) for compounds.

Theoretical and Experimental Studies of Gallate Melilite Electrides from Topotactic Reduction of Interstitial Oxide Ion Conductors

“…Typically theoretical analyses for electrides including the density of states, band structures, 3D charge distribution, and 2D electron localization function were performed with DFT calculations for melilite compositions. − More details on the DFT calculations are provided in the Supporting Information.…”

Discovery of Electrides in Electron‐Rich Non‐Electride Materials via Energy Modification of Interstitial Electrons

“…Sr 5 P 3 [ 8c ] and Ba 2 N 2 , [ 10b ] are highly desired. Recently, we have successfully realized the electrides characteristic in the electron‐deficient Ca 5 Pb 3 via pressurization and element doping, [ 13 ] suggesting the feasibility of the electronic engineering of the electron‐deficient materials to enrich the family of electrides. Recently, Zhu et al.…”

Design of semiconducting electrides via electron-metal hybridization: the case of Sc2C

“…Presently, just two rules for predicting electrides are widely accepted: (1) the metal atoms that form the coordination sphere around the electride electron must be electropositive 15 , and (2) the compound must be electron rich 16 . For example, in [Ca2N] + (e -) (17) , calcium is electropositive, and the compound is electron rich because the preferred oxidation states (Ca 2+ , N 3-) and stoichiometry provide an extra electron, forming an electride.…”