First‐Principles Study on Site Preference of Aluminum Vacancy and Nitrogen Atoms in γ–Alon

Abstract

The disorder in c-alon is caused by random arrangement of nitrogen atoms and aluminum vacancies. To understand the properties and electronic structure of c-alon by theoretical methods, the most reasonable structure model is needed. We examined the site preference of nitrogen atoms and aluminum vacancies by first-principles density functional theory (DFT) calculations on Al 24 O 24 N 8 and Al 23 O 27 N 5 . The calculated results for Al 24 O 24 N 8 with the lowest total energy indicated that nitrogen atoms prefer to be far away from each other, rather than in a completely random arrangement. The further investigation on Al 23 O 27 N 5 shows that the aluminum vacancies tend to possess octahedral sites and coordinate only with oxygen atoms. Evaluated by lattice variances (D a and D h ) and simulated XRD pattern, the most reasonable structure model of Al 23 O 27 N 5 has little deviation from the experimental results. The calculated bulk modulus of 200.9 GPa in Al 23 O 27 N 5 is slightly lower than the experimental value. The electronic structure reveals that the bonds of Al-N and Al-O have partially covalent and ionic characterization, while the covalent bond strength of Al-N is stronger than that of Al-O. The calculated band gap is 3.99 eV, which is much closer to the experimental 4.56 eV than previous suggestions. W.-Y. Ching-contributing editor Manuscript No. 32185.

First‐Principles Insight into the Composition‐Dependent Structure and Properties of γ‐Alon

“…This process leads to various configurations in the structure of γ‐alon. Our latest theoretical work and the previous reports demonstrated that the nitrogen atoms prefer to distribute far away from each other, and the aluminum vacancy prefers coordinating with oxygen atoms at the octahedral site in γ‐alon . The conclusion could guide the construction of supercell models of γ‐alon.…”

Photocatalytic properties of aluminum oxynitride (AlON)

“…Thus, the band gap of AlON here is estimated to be 5. AlON is a typical non-stoichiometry compound and crystal defects, such as aluminum vacancies are assumed in the AlON due to the deviation from the "ideal" composition [9][10][11][12][13]. As well known, a stable system requires the minimum potential.…”

“…A stable AlON is a non-stoichiometry compound and thus rich of defect structures. Both the theoretical calculation and experimental works evidenced that aluminum vacancies (V Al ′″ ) are predominant in AlON crystal and they are located at the octahedral sites [9][10][11][12][13]. These defects, which may occur during sintering process, will exert remarkable influence on the properties of AlON.…”

Critical Review—Narrow-Band Nitride Phosphors for Wide Color-Gamut White LED Backlighting

“…In addition, γ-AlON contains vacancies as regular part of the crystal, which are mainly distributed in the octahedral site. 39,40 When doped with Mn 2+ or rare earths, γ-AlON can be developed into interesting luminescent materials. Xie 41 The Mn 2+ -Mg 2+ co-doped sample yields 1.7 times of the emission intensity of the sample containing only Mn 2+ , and the emission band is red-shifted with the FWHM increasing from 32 to 44 nm (see Fig.…”