Effect of substitutional hydride ions on the charge states of oxygen vacancies in thermochemically reduced CaO and MgO

Chen, Y.; Orera, V. M.; González, R.; Williams, Richard; Williams, Gwyn; Rosenblatt, Gregg H.; Pogatshnik, G. J.

doi:10.1103/physrevb.42.1410

Cited by 39 publications

(28 citation statements)

References 19 publications

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“…The similarity of the F and F À energy levels in Fig. 3 despite the net charge difference is suggestive of the case of F þ and F centers in MgO addressed in a very recent first principles study [23] and earlier experiments [24]. In MgO (with divalent anion and cation), the absorption bands of the F þ center (one electron) and lattice-neutral F center (two electrons) are almost superimposed.…”

Section: Defect Formation Energies and Thermodynamic Transition Energiesmentioning

confidence: 71%

“…One important case for comparison is the one-and two-electron vacancy centers in MgO, termed F þ and F, respectively. These were the subject of a recent firstprinciples calculations [23] of optical spectra using the GW approach and the Bethe-Salpeter equation (BSE) aimed partly at elucidating the experimental observation [24] that the one-and two-electron centers in MgO have almost identical first optical absorption transitions, i.e., the optical binding energy of the second electron in the vacancy is almost the same as that of the first one. This might seem at first counter-intuitive in a static-lattice Coulomb potential picture.…”

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confidence: 99%

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First principles calculations and experiment predictions for iodine vacancy centers in SrI₂

Williams

Åberg

2013

Physica Status Solidi (b)

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We present the electronic structure, lattice relaxation, and formation energies of iodine vacancy defects in SrI 2 for the oneelectron, two-electron, and ionized charge states. We use a local generalized gradient approximation as well as non-local hybrid functionals within the framework of density functional theory, as it is commonly accepted that the latter can improve accuracy of the band gap and hence relevant energy levels. Comparison is made to published results on chlorine vacancy defects in NaCl calculated with similar methods and functionals, and also to a recent first-principles study of one-and two-electron occupancy in MgO vacancy centers. Using the parameters that are calculable from first principles in SrI 2 as a starting point, we incorporate available experimental data and adaptations of simple models to predict a range of results that can help guide or interpret future experiments such as absorption energy, configuration coordinate curves, vibrational lineshape, thermal trap depth, and Mollwo-Ivey comparison to alkaline-earth fluorides.Charge density contour in the F center in SrI 2 .

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Section: Defect Formation Energies and Thermodynamic Transition Energiesmentioning

confidence: 71%

mentioning

confidence: 99%

First principles calculations and experiment predictions for iodine vacancy centers in SrI₂

Williams

Åberg

2013

Physica Status Solidi (b)

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“…Despite its apparent simplicity, its properties as deduced from optical absorption and luminescence studies have proven somewhat ambiguous. Experimental characterization of the F-center in its neutral (F 0 ) and singly ionized (F +1 ) state has been complicated by their nearly identical optical absorption energies [25][26][27]. These energies have been corroborated by recent GW calculations [12]; however, these calculations also predicted optical emission energies that are substantially different from the assigned experimental values, causing the authors to suggest a reinvestigation of the experimental observations.…”

mentioning

confidence: 98%

“…The F-center defect (oxygen vacancy) in MgO is a typical example of an intrinsic point defect in a binary ionic compound [22][23][24][25][26][27]. Despite its apparent simplicity, its properties as deduced from optical absorption and luminescence studies have proven somewhat ambiguous.…”

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confidence: 99%

Point-defect optical transitions and thermal ionization energies from quantum Monte Carlo methods: Application to theF-center defect in MgO

2013

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We present an approach to calculation of point defect optical and thermal ionization energies based on the highly accurate quantum Monte Carlo methods. The use of an inherently many-body theory that directly treats electron correlation offers many improvements over the typically-employed density functional theory Kohn-Sham description. In particular, the use of quantum Monte Carlo methods can help overcome the band gap problem and obviate the need for ad-hoc corrections. We demonstrate our approach to the calculation of the optical and thermal ionization energies of the F-center defect in magnesium oxide, and obtain excellent agreement with experimental and/or other high-accuracy computational results.From electronics to optoelectronics to photovoltaics, point defects influence and even dominate the properties of semiconducting materials [1][2][3][4][5][6]. Quantitative descriptions of the effect of point defects on electronic, optical, and transport properties is critical to enabling point-defect engineering for materials design. However, accurate prediction of point-defect energetics, thermal ionization energies, and optical transition energies from first principles remains a challenge. Currently, the most widely-used approach based on conventional density functional theory (DFT) suffers from poor descriptions of band gaps that render difficult the accurate description of mid-gap defect states [5,[7][8][9]]. Here we demonstrate that, by contrast, an inherently many-body approach based on quantum Monte Carlo (QMC) methods [10,11] can eliminate these problems and enable high-accuracy calculations of point defect optical and thermal ionization energies. Our computed optical transition energies are in excellent agreement with experimental and/or other highaccuracy computational results for the same system [12], and demonstrate that QMC can obtain quantitatively accurate descriptions.

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“…In particular, the presence of oxygen vacancies in MgO and other alkaline-earth oxide single crystals has been established long ago and is one of the point defects most extensively studied. In the case of MgO, the oxygen vacancies are formed either by thermochemical reduction or by neutron irradiation: 34 these point defects are generally described as F centers, although different kinds of these centers exist depending on whether neutral atomic oxygen ͑F center͒, O Ϫ (F ϩ center͒, or O 2Ϫ (F 2ϩ center͒ is removed from the solid. In each case there are formally two, one, or zero electrons trapped in the cavity left by the removal of the oxygen species.…”

Section: Introductionmentioning

confidence: 99%

Theoretical study of bulk and surface oxygen and aluminum vacancies inα−Al2O3

2004

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The formation energy, geometry, and electronic structure of isolated oxygen and aluminum vacancies in bulk and on the ͑0001͒ surface of corundum (␣-Al 2 O 3 ) have been investigated by means of periodic calculations in the framework of density functional theory within the generalized gradient approximation and large supercells. The energy cost to form an oxygen vacancy in the bulk is estimated to be of the order of 10 eV, whereas that corresponding to the formation of Al vacancies is found to be at least a 30% larger. The relaxation of the material is rather small for both defects. The removal of an oxygen atom in bulk ␣-Al 2 O 3 is accompanied by the appearance of an impurity level in the gap, which is a strong indication of electron localization. This has been further confirmed by integration of the density of states in the energy interval corresponding to the impurity level and by several other theoretical analyses. For the ␣-Al 2 O 3 (0001) surface, the formation of oxygen and aluminum vacancies exhibits many similarities with the bulk; the energy cost to form Al vacancies is much larger than for O vacancies and, in both cases, it is accompanied by rather small atomic displacements. However, there are also significant differences between bulk and surface oxygen and aluminum vacancies. Thus the formation energy of one of these point defects in the surface is rather smaller as expected and, more importantly, the degree of electronic delocalization is also larger.

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Effect of substitutional hydride ions on the charge states of oxygen vacancies in thermochemically reduced CaO and MgO

Cited by 39 publications

References 19 publications

First principles calculations and experiment predictions for iodine vacancy centers in SrI₂

First principles calculations and experiment predictions for iodine vacancy centers in SrI₂

Point-defect optical transitions and thermal ionization energies from quantum Monte Carlo methods: Application to theF-center defect in MgO

Theoretical study of bulk and surface oxygen and aluminum vacancies inα−Al2O3

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Effect of substitutional hydride ions on the charge states of oxygen vacancies in thermochemically reduced CaO and MgO

Cited by 39 publications

References 19 publications

First principles calculations and experiment predictions for iodine vacancy centers in SrI2

First principles calculations and experiment predictions for iodine vacancy centers in SrI2

Point-defect optical transitions and thermal ionization energies from quantum Monte Carlo methods: Application to theF-center defect in MgO

Theoretical study of bulk and surface oxygen and aluminum vacancies inα−Al2O3

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First principles calculations and experiment predictions for iodine vacancy centers in SrI₂

First principles calculations and experiment predictions for iodine vacancy centers in SrI₂