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Sousa, Carmen; Graaf, Coen de; Illas, Francesc; Barriuso, M. T.; Aramburu, J. A.; Moreno, M.

doi:10.1103/physrevb.62.13366

Cited by 20 publications

(12 citation statements)

References 53 publications

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“…Indeed, CASPT2 has been successfully applied to study excited states in solid state compounds. [53][54][55][56][57][58] The active space used to construct the reference CASSCF wave functions includes the four vacancy orbitals involved in the lowest transitions, namely, one s-type and the three components of the p-like orbital, and two or one electron for the F and F + centers, respectively. 20 The CASSCF wave functions have been optimized for an average of the lowest four low-lying states, i.e., in a state-average CASSCF calculation.…”

Section: Methods Employed For the Study Of Excited States On Clustmentioning

confidence: 99%

First-principles study of the optical transitions ofFcenters in the bulk and on the (0001) surface ofα−Al2O3

et al. 2005

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The electronic structure and spectroscopic features of the optical spectra of oxygen vacancies in the bulk and on the ͑0001͒ surface of ␣-Al 2 O 3 have been studied by first-principles methods. The effect of oxygen vacancies on the crystalline structure has been determined by the appropriate atomic structure optimization carried out using a periodic model and density functional theory ͑DFT͒ calculations. Both, neutral ͑F center͒ and charged ͑F + center͒ oxygen vacancies have been considered. Optical transitions arising from the excitations of the electron͑s͒ trapped in the F + and F centers, both on the surface and in the bulk of the material, have been studied using a suitable embedded cluster model approach. The cluster geometry, including the relaxation around the vacancy, has been taken from the periodic calculations. The transition energies and intensities have been obtained by applying the explicitly correlated multiconfigurational second-order perturbation theory method and also time-dependent DFT approaches. The present results are in good agreement with available experimental data for the bulk and provide a guide to interpret forthcoming experiments involving the spectroscopy of oxygen vacancies present in irradiated or defective ␣-Al 2 O 3 ͑0001͒ surfaces.

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Section: Methods Employed For the Study Of Excited States On Clustmentioning

confidence: 99%

First-principles study of the optical transitions ofFcenters in the bulk and on the (0001) surface ofα−Al2O3

et al. 2005

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“…[40][41][42][43] The method has also been successfully applied to study excited states in solid state compounds. [44][45][46] The construction of the CASSCF wave functions has been performed in the C s point group symmetry. To avoid convergence problems and to ensure orthogonal ground and excited states, the CASSCF wave functions have been optimized for an average of states for each irreducible representation of the C s point group symmetry, AЈ and AЉ.…”

Section: Computational Detailsmentioning

confidence: 99%

Optical properties of peroxy radicals in silica: Multiconfigurational perturbation theory calculations

Sousa

Graaf

Pacchioni

2001

The Journal of Chemical Physics

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The low-lying electronic transitions in a peroxy radical, wSi-O-O • , a fundamental radiation induced point defect in silicon dioxide, have been investigated by means of ab initio multiconfiguration perturbation theory calculations, CASPT2, and cluster models. The accuracy of the computed transition energies and intensities as predicted by the CASPT2 approach has been checked by studying the exited state properties of two molecular analogues, the HOO • and CH 3 OO • radicals, and of a well-characterized paramagnetic defect in silica, the nonbridging oxygen center, wSi-O • , for which unambiguous assignments exist. We found that the peroxy radical gives rise to two optical absorption bands, a very weak one at 0.7 eV and an intense one at 5.49 eV, in agreement with the experimental assignments of Radzig ͓V. A. Radzig, Chem. Phys. Reports 14, 1206 ͑1995͔͒.

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“…The band in the longer wavelength portion of this 370 nm feature is assigned to the electric-dipole-allowed 4d 10 5s 1 to 4d 10 5p 1 transition of the Ag 0 center [26]. This 4d 10 5p 1 excited state has a delocalized character and is near, or possibly in, the conduction band [29,30]. Thus, stimulation wavelengths within this band easily release trapped electrons from the Ag 0 centers.…”

Section: Optical Absorptionmentioning

confidence: 99%

Optically stimulated luminescence (OSL) from Ag-doped Li2B4O7 crystals

Kananen

Maniego

Golden

et al. 2016

Journal of Luminescence

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a b s t r a c tOptically stimulated luminescence (CW-OSL) is observed from Ag-doped lithium tetraborate (Li 2 B 4 O 7 ) crystals. Photoluminescence, optical absorption, and electron paramagnetic resonance (EPR) are used to identify the defects participating in the OSL process. As-grown crystals have Ag þ ions substituting for Li þ ions. They also have Ag þ ions occupying interstitial sites. During a room-temperature exposure to ionizing radiation, holes are trapped at the Ag þ ions that replace Li þ ions and electrons are trapped at the interstitial Ag þ ions, i.e., the radiation forms Ag 2 þ (4d 9 ) ions and Ag 0 (4d 10 5s 1 ) atoms. These Ag 2 þ and Ag 0 centers have characteristic EPR spectra. The Ag 0 centers also have a broad optical absorption band peaking near 370 nm. An OSL response is observed when the stimulation wavelength overlaps this absorption band. Specifically, stimulation with 400 nm light produces an intense OSL response when emission is monitored near 270 nm. Electrons optically released from the Ag 0 centers recombine with holes trapped at Ag 2 þ ions to produce the ultraviolet emission. The OSL response is progressively smaller as the stimulation light is moved to longer wavelengths (i.e., away from the 370 nm peak of the absorption band of the Ag 0 electron traps). Oxygen vacancies are also present in the Ag-doped Li 2 B 4 O 7 crystals, and their role in the OSL process as a secondary relatively short-lived electron trap is described.

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Neutral atoms in ionic lattices: Excited states ofKCl:Ag0

Cited by 20 publications

References 53 publications

First-principles study of the optical transitions ofFcenters in the bulk and on the (0001) surface ofα−Al2O3

First-principles study of the optical transitions ofFcenters in the bulk and on the (0001) surface ofα−Al2O3

Optical properties of peroxy radicals in silica: Multiconfigurational perturbation theory calculations

Optically stimulated luminescence (OSL) from Ag-doped Li2B4O7 crystals

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