Infra-red, electron paramagnetic resonance and X-ray photoemission spectral properties of point defects in silica from first-principle calculations

Pacchioni, Gianfranco; Vitiello, Mirko

doi:10.1016/s0022-3093(98)00888-6

Cited by 11 publications

(5 citation statements)

References 36 publications

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“…This conclusion is consistent with observations in a previous investigation of EЈ-type centers, 39,70 in which a stronger spin-localization tendency of the Hartree-Fock scheme was observed. Indeed, this tendency explains the behavior of the differences as a function of the number of first-neighbor oxygen atoms.…”

Section: A Hartree-fock Vs Density Functionalsupporting

confidence: 93%

“…Pacchioni and Vitiello addressed the EЈ center using similar clusters and a hybrid gradient-corrected density-functional methodology. 39 Using cluster calculations, Uchino et al showed that their alternative model for the EЈ center also reproduced the experimental hyperfine splittings. 17,18 Boero et al studied a model for the E ␥ Ј center within a density-functional approach starting from a periodically repeated model structure of vitreous SiO 2 generated by first-principles molecular dynamics.…”

Section: Introductionmentioning

confidence: 97%

“…30 From the theoretical side, the S and X centers have been given only modest attention, wheareas the EЈ center both in ␣ quartz and in amorphous SiO 2 has been the subject of numerous semiempirical 5,31-33 and ab initio calculations. 17,18,34 -47 Among the ab initio studies, only a few addressed ESR parameters 17,18,35,39,40,45,46 and even less aimed at modeling the amorphous environment. 17,18,35,[39][40][41] Karna and Kurtz 40,42 performed Hartree-Fock calculations on very small model clusters to predict hyperfine data for the EЈ center and its oxygen-deficient variants.…”

Section: Introductionmentioning

confidence: 99%

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First-principles modeling of paramagnetic Si dangling-bond defects in amorphousSiO2

Stirling

Pasquarello

2002

Phys. Rev. B

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We modeled paramagnetic Si dangling-bond defects in amorphous SiO 2 using a generalized-gradient density-functional approach. By creating single oxygen vacancies in a periodic model of amorphous SiO 2 , we first generated several model structures in which the core of the defect consists of a threefold coordinated Si atom carrying a dangling bond. These model structures were then fully relaxed and the hyperfine parameters calculated. We found that the hyperfine parameters of such model defects, in both the neutral and positive charge states, reproduced those characteristic of the EЈ, in accord with experimental observations for amorphous SiO 2 . By eliminating a second O atom in the nearest-neighbor shell of these defect centers, we then generated model defects in which the Si atom carrying the dangling bond forms bonds with two O atoms and one Si atom. In this defect, the spin density is found to delocalize over the Si-Si dimer bond, giving rise to two important hyperfine interactions. These properties match the characteristics of the hyperfine spectrum measured for the S center. Our results are complemented by the calculation of hyperfine interactions for small cluster models which serve the threefold purpose of comparing different electronic-structure schemes for the calculation of hyperfine interactions, estimating the size of core-polarization effects, and determining the reliability of cluster approximations used in the literature.

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Section: A Hartree-fock Vs Density Functionalsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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First-principles modeling of paramagnetic Si dangling-bond defects in amorphousSiO2

Stirling

Pasquarello

2002

Phys. Rev. B

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“…This technique allows quantifying paramagnetic defects, and can also give qualitative information from the line shape: signal anisotropy and hyperfine splitting constant (A) allow identification of the chemical nature of the paramagnetic center. Hyperfine splitting can yield valuable information on coupling with neighboring 17 O and 29 Si. , For instance, hyperfine splittings were correlated with Si–O–Si in a recent study …”

Section: Experimental Datamentioning

confidence: 99%

Silica Surface Features and Their Role in the Adsorption of Biomolecules: Computational Modeling and Experiments

et al. 2013

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“…Coexistence of different local arrangements leads to defect formation in the structure, impacting significantly the main physical properties, i.e., bandgap (Egap) value. [45][46][47][48] The various types and number of orthosilicate anions (from 1 to 20) were used to design fused silica. The dangling bonds of the molecular system were saturated by H atoms, a commonly used technique to "embed" clusters of the semiconducting or insulating materials.…”

Section: Resultsmentioning

confidence: 99%

Ultrafast bandgap narrowing and cohesion loss of photoexcited fused silica

Tsaturyan

Kachan

Stoian

et al. 2022

The Journal of Chemical Physics

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Coupling and spatial localization of energy on the timescale of the excitation pulse in ultrashort laser irradiated dielectric materials are key elements for enabling processing precision beyond the optical limit. We apply a first-principles model to determine dynamic distortions of energy bands following the rapid increase in the free-carrier population in an amorphous dielectric excited by an ultrashort laser pulse. Fused silica glass is reproduced using a system of (SiO4)4- tetrahedra, where DFT extended to FT-DFT reproduces ground and photoexcited states. Triggered by electronic charge redistribution, a bandgap narrowing of more than 2 eV is shown to occur in fused silica under geometry relaxation. Calculations reveal that the bandgap decrease results from the rearrangement of atoms altering the bonding strength. Despite an atomic movement impacting strongly the structural stability, the observed change of geometry remains limited to 7% of the interatomic distance and occurs on the femtosecond timescale. This structural relaxation is thus expected to take place quasi-instantly following the photon energy flux. Moreover, under intense laser excitation, fused silica loses its stability when an electron temperature of around 2.8 eV is reached. Further increase of the excitation energy leads to the collapse of both structure and bandgap.

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Infra-red, electron paramagnetic resonance and X-ray photoemission spectral properties of point defects in silica from first-principle calculations

Cited by 11 publications

References 36 publications

First-principles modeling of paramagnetic Si dangling-bond defects in amorphousSiO2

First-principles modeling of paramagnetic Si dangling-bond defects in amorphousSiO2

Silica Surface Features and Their Role in the Adsorption of Biomolecules: Computational Modeling and Experiments

Ultrafast bandgap narrowing and cohesion loss of photoexcited fused silica

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