TY - JOUR
T1 - Localisation assisted by the lattice relaxation and the optical absorption of extra-framework electrons in 12CaO•Al 2O 3
AU - Sushko, Peter V.
AU - Shluger, Alexander L.
AU - Hayashi, Katsuro
AU - Hirano, Masahiro
AU - Hosono, Hideo
N1 - Funding Information:
We wish to thank J. Gavartin, T. Kamiya, I. V. Abarenkov, A. M. Stoneham for valuable discussions. This work is supported by Japanese Science and Technology Agency and by the Grant-in-Aid for Creative Scientific Research No. 16GS0205 from Japanese Ministry of Education, Culture, Sports, Science and Technology. The computer time on the HPCx facility was awarded to the Materials Chemistry consortium under EPSRC grant GR/S13422/01 ‘Materials Chemistry Using Tera-Scale computing’.
PY - 2005/12
Y1 - 2005/12
N2 - 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.
AB - 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.
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U2 - 10.1016/j.msec.2005.06.047
DO - 10.1016/j.msec.2005.06.047
M3 - Article
AN - SCOPUS:27744577026
SN - 0928-4931
VL - 25
SP - 722
EP - 726
JO - Materials Science and Engineering C
JF - Materials Science and Engineering C
IS - 5-8
ER -