Electronic structure of α-Al2O3: Ab initio simulations and comparison with experiment

“…More interestingly, three of these clusters have a positive LUMO eigenvalue suggesting that they would not accept an additional electron from the vacuum, and the electron affinities Figure 12. GW spectra (Gaussian smeared) for 10 (Al 2 O 3 ) 4 local minimum clusters shown next to their respective ball-and-stick models, the Boltzmann-weighted superposition of these spectra (top two graphs); and for bulk alumina, experimental data (black lines) for X-ray emission and absorption spectra taken from Perevalov et al (2007) (top left graph), ultraviolet photoelectron spectrum taken from Perevalov et al (2007) (top right) and X-ray photoelectron spectrum taken from Tagle et al (1979) and Balzarotti & Bianconi (1976) (top right, smooth curve). The intensities are in arbitrary units and energy spans from −20 to +5 eV.…”

Section: Resultsmentioning

confidence: 99%

Atomistic and electronic structure of (X ₂ O ₃ ) _n nanoclusters; n =1–5, X=B, Al, Ga, In and Tl

Woodley

2011

Proc. R. Soc. A.

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The stable and metastable, as measured using an all-electron density functional theory approach, stoichiometric clusters of boron, aluminium, gallium, indium and thallium oxide are reported. Initial candidate structures were found using an evolutionary algorithm to search the energy landscape, defined using classical interatomic potentials, for alumina and india followed by data mining or rescaling. Characterization of the refined structures was performed by electronic structure techniques at the hybrid density functional and many-body GW levels of theory. We make accurate predictions of the spectroscopic properties represented by mean ionization potentials of 11.4, 9.9, 9.8, 8.8 and 8.4 eV and electron affinities of 0.05, 1.1, 1.6, 1.9 and 2.5 eV for boria, alumina, gallia, india and thallia, respectively. The changes in the global minima, atomistic and electronic properties with respect to the cluster and cation size are discussed.

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“…Practically, when the mixing parameter of = 0.04 was used in every iteration step, we reached within It is generally believed that the momentum dependence of the dielectric function in α-Al 2 O 3 is small because its valence electron band is quite flat [14]. In this situation, the influence of the retardation effect is reduced by acquiring the VEEL spectra with a larger collection semi-angle to dampen the retardation effect.…”

Section: Methodsmentioning

confidence: 90%

Improving the measurement of dielectric function by TEM-EELS: avoiding the retardation effect

2016

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We investigated an improved Kramers-Kronig analysis (KKA) routine for measuring the dielectric function of α-Al 2 O 3 , avoiding the retardation effect arising in electron energy-loss spectroscopy (EELS). The EELS data differed from the optical data in the energy range of 10-20 eV due to the retardation effect, even though Cerenkov loss was thoroughly suppressed. The calculated differential cross-section indicates that the influence of the retardation appears at scattering angles less than 0.2 mrad in the loss energy range of 10-15 eV. Using the improved KKA routine, we obtained the correct dielectric function that agreed with the optical data. The present technique is especially useful in measuring the dielectric function by EELS with a small collection semi-angle.

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Electronic structure of α-Al2O3: Ab initio simulations and comparison with experiment

Cited by 91 publications

References 13 publications

Modeling the charge transport mechanism in amorphous Al2O3 with multiphonon trap ionization effect

Modeling the charge transport mechanism in amorphous Al2O3 with multiphonon trap ionization effect

Atomistic and electronic structure of (X ₂ O ₃ ) _n nanoclusters; n =1–5, X=B, Al, Ga, In and Tl

Improving the measurement of dielectric function by TEM-EELS: avoiding the retardation effect

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Electronic structure of α-Al2O3: Ab initio simulations and comparison with experiment

Cited by 91 publications

References 13 publications

Modeling the charge transport mechanism in amorphous Al2O3 with multiphonon trap ionization effect

Modeling the charge transport mechanism in amorphous Al2O3 with multiphonon trap ionization effect

Atomistic and electronic structure of (X 2 O 3 ) n nanoclusters; n =1–5, X=B, Al, Ga, In and Tl

Improving the measurement of dielectric function by TEM-EELS: avoiding the retardation effect

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Atomistic and electronic structure of (X ₂ O ₃ ) _n nanoclusters; n =1–5, X=B, Al, Ga, In and Tl