Abstract
γ-Al2O3 is a porous metal oxide and described as a defective spinel with some cationic vacancies. In this work, we calculate the electronic density of states and band structure for the bulk of this material. The calculations are performed within the density functional theory using the full potential augmented plan waves plus local orbital method, as embodied in the WIEN2k code. We show that the modified Becke-Johnson exchange potential, as a semi-local method, can predict the bandgap in better agreement with the experiment even compared to the accurate but much more expensive green function method. Moreover, our electronic structure analysis indicates that the character of the valence band maximum mainly originates from the p orbital of those oxygen atoms that are close to the vacancy. The charge density results show that the polarization of the oxygen electron cloud is directed toward aluminum cations, which cause Al and O atoms to be tightly connected by a strong dipole bond.
Highlights
All of the calculations in this work were carried out using the WIEN2K code [8], which is based on the full potential augmented plane waves plus local orbital method
We have successfully simulated the γ-Al2O3 compound based on the density functional theory (DFT) method using the full potential augmented plan waves plus local orbital method, as embodied in the WIEN2k code, and applied the mBJ exchange potential on this system to predict its bandgap more precisely
We showed that distribution of the valence charge density is not uniform around different Al lattice sites
Summary
Methods All of the calculations in this work were carried out using the WIEN2K code [8], which is based on the full potential augmented plane waves plus local orbital method. We have used the mBJ exchange potential to investigate the electronic structure and bandgap of bulk γ-Al2O3. This functional has been proposed by Tran and Blaha [7]. The perfect crystalline structure of γ-Al2O3 is described as a defective spinel, denoted as □223Al2113O32, ( = Al vacancy) [5,11]. The space symmetry group of a perfect spinel, such as the MgAl2O4 structure, is Fd3m In this symmetry group, the primitive cell is a triclinic cell of 14 atoms, and it is denoted as. Atom triclinic cell containing eight Al2O3 formula units and two Al vacancies is obtained.
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