Electron Localization and a Confined Electron Gas in Nanoporous Inorganic Electrides

The nanoporous main group oxide $12\mathrm{C}\mathrm{a}\mathrm{O}·7{\mathrm{A}\mathrm{l}}_2{\mathrm{O}}_3$ (C12A7) can be transformed from a wide-gap insulator to an electride where electrons substitute anions in cages constituting a positive frame. Our ab initio calculations of the electronic structure of this novel material give a consistent explanation of its high conductivity and optical properties. They show that the electrons confined in the inert positive frame are localized in cages and undergo hopping between neighboring cages. The results are useful for the understanding of behavior of confined electron gas of different topology and electron-phonon coupling, and for designing new transparent conductors, electron emitters, and electrides.

Figure 1

The setup of embedded cluster calculation: The quantum cluster including two cages is in the middle surrounded by regions I and II of classical ions. Only half of the classical ions are shown for clarity.

Figure 2

The isosurface of the wave function of the electron localized in one of the C12A7 cages.

Figure 3

Schematic of the energy levels of the system showing the optical transitions and character of electronic states.