Localisation assisted by the lattice relaxation and the optical absorption of extra-framework electrons in 12CaO•Al 2O 3

Peter V. Sushko, Alexander L. Shluger, Katsuro Hayashi, Masahiro Hirano, Hideo Hosono

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)

Abstract

The crystalline framework of a complex oxide 12CaO•7Al 2O 3 (C12A7) is built from positively charged sub-nanometer cages able to trap electrons. An embedded cluster approach is used to study the electronic structure and optical properties of electron-containing C12A7 for different concentration of extra-framework electrons. Our results suggest that the conduction band of the C12A7 consists of a relatively narrow band of empty cage states (cage conduction band) with one-electron energies between 5.5 and 6.1 eV above the top of the valence band (VB), and a framework conduction band at about 6.7 - 7.0 eV above the to of the VB. The gap between the cage conduction band and the framework conduction band is estimated to be about 1 - 1.5 eV. The energies of the lowest optical transitions from the top of the valence band to the cage conduction band are predicted to be at 5.2 - 5.5 eV. The extra-electrons occupy cage states, which split from the cage conduction band to about 4 eV above the top of the VB. The extra-framework electrons introduce two absorption bands with the experimental peaks at 0.4 eV and 2.8 eV. These bands are assigned to the inter-cage charge transfer and the intra-cage s-p transitions respectively. The changes in the optical absorption spectra as a function of the extra-electrons concentration are also discussed.

Original languageEnglish
Pages (from-to)722-726
Number of pages5
JournalMaterials Science and Engineering C
Volume25
Issue number5-8
DOIs
Publication statusPublished - Dec 1 2005
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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