The oxygen vacancy at the surface and in bulk MgO: An embedded-cluster study

Scorza, Erminia; Birkenheuer, U.; Pisani, Cesare

doi:10.1063/1.475260

Cited by 143 publications

(142 citation statements)

References 39 publications

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“…The region directly adjacent to the cluster border requires special attention in order to describe correctly the behaviour of the electrons confined inside the QM cluster. Several techniques of different complexity have been suggested (see, for example, [19,20,21,22,23,24]) none of which is completely satisfactory. For ionic systems, such as NaCl, MgO, CaO, using effective core pseudopotentials on cations surrounding the QM cluster usually provides reliable results [24,25].…”

Section: Methods Of Calculationsmentioning

confidence: 99%

“…[12,13,14,15,16,17,18]). Several types of embedded cluster techniques have been used successfully to study the structure and properties of defects in ionic oxides, such as MgO (see, for example, [19,20,21,22,23,24]), CaO [25] and SiO 2 [26,27]. In this paper we use an embedded cluster model to study defects in YSZ and calculate their spectroscopic properties.…”

Section: Introductionmentioning

confidence: 99%

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Structure and spectroscopic properties of oxygen divacancy in yttrium-stabilized zirconia

Ramo

Shluger

2008

J. Phys.: Conf. Ser.

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Abstract. We have studied the structure and spectroscopic properties of the oxygen divacancy defect in Yttrium-stabilized ZrO2 using periodic and embedded cluster methods and GGA and B3LYP density functionals. The results demonstrate that the defect spectroscopic properties depend on the particular arrangement of Y dopants near vacancies. The optical transition energies calculated for the negatively charged state of the divacancy at 2.8 eV and 3.3 eV are in agreement with experimental data. The second set of transitions between 1.9 eV and 2.7 eV corresponds to the electron transfer between vacancies. The calculated EPR g-tensor values are in agreement with other works. The results support the proposed attribution of the optical absorption peaking at 3.3 eV and related EPR spectra to Zr 3+ ions in the YSZ matrix, however, they are not fully conclusive due to dependence on Y concentration.

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Section: Methods Of Calculationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Structure and spectroscopic properties of oxygen divacancy in yttrium-stabilized zirconia

Ramo

Shluger

2008

J. Phys.: Conf. Ser.

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“…Defects play a very important role in the chemistry of oxide surfaces. 77 The are various kinds of point defects that can be found on an oxide surface: low-coordinated cations and anions, 48 isolated cation 78 and anion vacancies, [79][80][81][82] . At high concentrations of cation or anion vacancies, it is more appropriate to refer to the system as non-stoichiometric.…”

Section: Defective Oxide Surfacesmentioning

confidence: 99%

Controlling the charge state of supported nanoparticles in catalysis: lessons from model systems

2018

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Model systems are very important to identify the working principles of real catalysts, and to develop concepts that can be used in the design of new catalytic materials. In this review we report examples of the use of model systems to better understand and control the occurrence of charge transfer at the interface between supported metal nanoparticles and oxide surfaces. In the first part of this article we concentrate on the nature of the support, and on the basic difference in metal/oxide bonding going from a wide-gap non-reducible oxide material to reducible oxide semiconductors. The roles of oxide nanostructuring, bulk and surface defectiveness, and doping with hetero-atoms are also addressed, as they are all aspects that severely affect the metal/oxide interaction. Particular attention is given to the experimental measures of the occurrence of charge transfer at the metal/oxide interface. In this respect, systems based on oxide ultrathin films are particularly important as they allow the use of scanning probe spectroscopies which, often in combination with other measurements and with first principles theoretical simulations, allow full characterization of small supported nanoparticles and their charge state. In a few selected cases, a precise count of the electrons transferred between the oxide and the supported nanoparticle has been possible. Charge transfer can occur through thin, two-dimensional oxide layers also thanks to their structural flexibility. The flow of charge through the oxide film and the formation of charged adsorbates are accompanied in fact by a substantial polaronic relaxation of the film surface which can be rationalized based on electrostatic arguments. In the final part of this review the relationships between model systems and real catalysts are addressed by discussing some examples of how lessons learned from model systems have helped in rationalizing the behavior of real catalysts under working conditions.

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“…For example, the spectroscopic features of O vacancies in MgO bulk and at the MgO͑001͒ surface have been investigated at length. In this simple material, the very small geometric relaxation around the vacancy, as predicted either by cluster model 21 or periodic calculations, 22 and the strongly localized nature of the ground and excited states related to the trapped electrons left upon oxygen removal 21,23 was profited to define a properly embedded cluster. The main advantage of cluster models to periodic supercell approaches is that on the former sophisticated, explicitly correlated, ab initio wave-function-based methods can be applied simultaneously to the ground and excited states These techniques allow one to compute the energy transitions from the ground to the low-lying excited states and the corresponding oscillator strengths, thus providing information for the proper assignment of the spectroscopic features of interest.…”

Section: Introductionmentioning

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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The oxygen vacancy at the surface and in bulk MgO: An embedded-cluster study

Cited by 143 publications

References 39 publications

Structure and spectroscopic properties of oxygen divacancy in yttrium-stabilized zirconia

Structure and spectroscopic properties of oxygen divacancy in yttrium-stabilized zirconia

Controlling the charge state of supported nanoparticles in catalysis: lessons from model systems

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

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