Probability-based threshold displacement energies for oxygen and silicon atoms in α-quartz silica

Cowen, Benjamin

doi:10.1016/j.commatsci.2015.12.041

Cited by 20 publications

(8 citation statements)

References 39 publications

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“…of one or more Si or O atoms from their initial lattice positions. Cowen et al recently calculated displacement probabilities for Si and O atoms in silica for a wide range of initial atomic kinetic energies and angles, validating their results against previous theory and experimental displacement data 28. The energies required to give 1% displacement probability for O and Si atoms are ∼11 and ∼25 eV, respectively, and for 33% displacement probability the energies are ∼25 and ∼50 eV, for…”

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Inherent Size Effects on XANES of Nanometer Metal Clusters: Size-Selected Platinum Clusters on Silica

et al. 2016

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X-ray absorption near-edge structure (XANES) is commonly used to probe the oxidation state of metal-containing nanomaterials; however, as the particle size in the material drops below a few nanometers, it becomes important to consider inherent size effects on the electronic structure of the materials. In this paper, we analyze a series of size-selected Pt n /SiO2 samples, using X-ray photoelectron spectroscopy (XPS), low energy ion scattering, grazing-incidence small-angle X-ray scattering, and XANES. The oxidation state and morphology are characterized both as-deposited in UHV, and after air/O2 exposure and annealing in H2. The clusters are found to be stable during deposition and upon air exposure, but sinter if heated above ∼150 °C. XANES shows shifts in the Pt L3 edge, relative to bulk Pt, that increase with decreasing cluster size, and the cluster samples show high white line intensity. Reference to bulk standards would suggest that the clusters are oxidized; however, XPS shows that they are not. Instead, the XANES effects are attributable to development of a band gap and localization of empty state wave functions in small clusters.

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confidence: 72%

Inherent Size Effects on XANES of Nanometer Metal Clusters: Size-Selected Platinum Clusters on Silica

et al. 2016

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“…It has detachments points of 0.5 and 1.54 Å for the O-Si interactions, and 0.4 and 2.1 Å for the O-O interactions [35]. This splined BKS and ZBL potential has been used successfully in earlier MD simulations of crystalline silica by these authors [35] for determining the TDE probability distributions for the oxygen and silicon PKAs in α-quartz. In this potential, Coulomb interactions are simulated using the particle-particle particle-mesh (PPPM) solver, with a relative error of 1.0 × 10 −6 .…”

Section: Methodsmentioning

confidence: 99%

“…MD simulations for characterizing irradiation effects in α-quartz have focused on estimating the TDEs of the oxygen and silicon PKAs and the point defects produced [35,36]. Cowen and El-Genk [35] have used a BKS-ZBL force field successfully, for short (5.5 Å) and long (15 Å) cutoffs, to calculate the probability distributions for threshold displacement energy (TDE) for oxygen and silicon PKAs, up to 150 eV [32]. Wang et al [36] reported single TDE values for the oxygen and silicon atoms of 28.9 and 70.5 eV, respectively.…”

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Estimates of point defect production inα-quartz using molecular dynamics simulations

Cowen

2017

Modelling Simul. Mater. Sci. Eng.

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Molecular dynamics (MD) simulations are performed to investigate the production of point defects in α-quartz by oxygen and silicon primary knock-on atoms (PKAs) of 0.25–2 keV. The Wigner–Seitz (WS) defect analysis is used to identify the produced vacancies, interstitials, and antisites, and the coordination defect analysis is used to identify the under and over-coordinated oxygen and silicon atoms. The defects at the end of the ballistic phase and the residual defects, after annealing, increase with increased PKA energy, and are statistically the same for the oxygen and silicon PKAs. The WS defect analysis results show that the numbers of the oxygen vacancies and interstitials (VO, Oi) at the end of the ballistic phase is the highest, followed closely by those of the silicon vacancies and interstitials (VSi, Sii). The number of the residual oxygen and silicon vacancies and interstitials are statistically the same. In addition, the under-coordinated OI and SiIII, which are the primary defects during the ballistic phase, have high annealing efficiencies (>89%). The over-coordinated defects of OIII and SiV, which are not nearly as abundant in the ballistic phase, have much lower annealing efficiencies (<63%) that decrease with increased PKA energy.

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“…Recently, MD simulations have been used to estimate the TDEs for metal oxides and other materials, using different potentials [30,[34][35][36][37]. The simulations employ interatomic potentials and Newton's equations of motion to update the positions of the atoms in a domain of many thousands to billions of atoms of the material of interest.…”

Section: Introductionmentioning

confidence: 99%

Directional dependence of the threshold displacement energies in metal oxides

Cowen

2017

Modelling Simul. Mater. Sci. Eng.

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Molecular dynamics (MD) simulations are performed to investigate the directional dependence and the values of the threshold energies (TDEs) for the displacements of the oxygen and metal atoms and for producing stable Frenkel pairs in five metal oxides of Cr2O3, Al2O3, TiO2, SiO2, and MgO. The TDEs for the Frenkel pairs and atoms displacement are calculated in 66 crystallographic directions, on both the anion and cation sublattices. The performed simulations are for metal and oxygen PKA energies up to 350 and 400 eV, respectively. The calculated probability distributions for the atoms displacement and average number of Frenkel pairs produced in the different oxides are compared. The results revealed unique symmetrical patterns of the TDEs for the displacement of the atoms and the formation of stable Frenkel pairs, confirming the strong dependence on the direction and the crystalline structure of the oxides. Results also showed that the formation of stable Frenkel pairs is associated with the displacements of the PKAs and/or of the SKAs. The probabilities of the TDEs for the displacement of the oxygen and metal PKAs are consistently lower than those of the atoms in the crystal. In SiO2, TDEs for the displacement of oxygen and metal atoms and those for the formation of stable Frenkel pairs are the lowest, while those in TiO2 are among the highest. The results for Cr2O3 and Al2O3, which have the same crystal structure, are similar. The calculated TDEs for MgO, Al2O3 and TiO2 are generally in good agreement with the experimental values and the probability distributions of the TDEs for the PKAs in TiO2 are in good agreement with reported MD simulation results.

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Probability-based threshold displacement energies for oxygen and silicon atoms in α-quartz silica

Cited by 20 publications

References 39 publications

Inherent Size Effects on XANES of Nanometer Metal Clusters: Size-Selected Platinum Clusters on Silica

Inherent Size Effects on XANES of Nanometer Metal Clusters: Size-Selected Platinum Clusters on Silica

Estimates of point defect production inα-quartz using molecular dynamics simulations

Directional dependence of the threshold displacement energies in metal oxides

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