Optical Absorption near the Absorption Edge in V<sub>2</sub>O<sub>5</sub> Single Crystals

Bodó, Z.; Hevesi, I.

doi:10.1002/pssb.19670200153

Cited by 33 publications

(20 citation statements)

References 3 publications

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“…6 has been given in the short note [2]. It was found that the absorption coefficients in the long wave-tail of the absorption edge follow URBACH'S rule K = K 0 exp fl -~ [7], i.e.…”

Section: Discussionmentioning

confidence: 99%

“…normally to the c axis ( 3_ polarization). As described in [2], absorption coefficients in the region of the intrinsic edge have been calculated on the basis of the following formula for the average transmission:…”

Section: Experimental Equipment and Methodsmentioning

confidence: 99%

“…In the present paper we wish to present some further results of our work connected with our investigations briefly described in the short note [2].…”

Section: Introductionmentioning

confidence: 99%

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On the optical properties of vanadium pentoxide single crystals

Hevesi

1967

Acta Physica

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“…6 has been given in the short note [2]. It was found that the absorption coefficients in the long wave-tail of the absorption edge follow URBACH'S rule K = K 0 exp fl -~ [7], i.e.…”

Section: Discussionmentioning

confidence: 99%

Section: Experimental Equipment and Methodsmentioning

confidence: 99%

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On the optical properties of vanadium pentoxide single crystals

Hevesi

1967

Acta Physica

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“…42,43 The lattice relaxation that occurs at the V 2 O 5 ͑001͒ surface upon reduction produces distinct changes in the surface electronic structure. Figure 8 compares the spin-projected total density of states of the isolated defect ͑1 ϫ 3͒-O vac 1 structure at 1 / 6 ML [ Fig.…”

Section: O-vacancy-induced Electronic Effectsmentioning

confidence: 99%

Stability of reducedV2O5(001)surfaces

2004

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The defect-free V 2 O 5 ͑001͒ surface and ordered structures involving oxygen vacancies have been studied for a wide range of defect concentrations, ⌰ (1/6ഛ⌰ഛ1 monolayer, ML), combining density functional theory and statistical thermodynamics. At ⌰ =1/4 ML the oxygen vacancy formation energy for the singly coordinated surface oxygen atoms (vanadyl oxygen, O 1 ) is by ϳ1.7 eV/ atom and ϳ2.0 eV/ atom lower than the corresponding values for two-and threefold coordinated surface oxygen atoms, respectively. Between 1 / 3 and 1 / 2 ML the alignment of vanadyl oxygen vacancies ͑O vac 1 ͒ along the [010] direction is by 70 meV/ atom ͑⌰ =1/3 ML͒ and 120 meV/ atom ͑⌰ =1/2 ML͒ more favorable than along the [100] direction, with the concentration-induced change of the vacancy formation energy for structures with vacancies aligned along the [100] direction being smaller than 20 meV/ atom. The lowest vacancy formation energy of 1.87 eV/ atom corresponds to the ͑1 ϫ 1͒-O vac 1 ͑⌰ =1/2 ML͒ phase with defects forming a trenchlike structure with rows along the [010] direction. Above 1 / 2 ML the vacancy formation energy increases up to 2.07 eV/ atom ͑⌰ =1 ML͒. The ease of formation of nonrandom vacancy structures with a favored alignment along the [010] direction is discussed in terms of special vacancy-induced lattice distortions. It is also argued that the trenches along the [010] direction provide preferred paths for continuous reduction of the surface starting from isolated defect sites. However, this missing-row structure would be stable only at very low oxygen partial pressures close to conditions for which V 2 O 5 decomposes into VO 2 and O 2 .

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“…In addition, Magnéli phases such as V 3 O 7 , V 4 O 9 , and V 6 O 13 , also occur [130]. V 2 O 5 is an insulator with a direct optical band gap of *2.3 eV [131,132]. On the V 2 O 5 (001) surface there are three structurally different oxygen atoms in each layer: vanadyl oxygen, O 1 , coordinated to one vanadium atom, bridging oxygen atoms, O 2 , and threefold coordinated oxygen atoms, O 3 , respectively (cf.…”

Section: Experimental Findings On Oxygen Defectsmentioning

confidence: 97%

Oxygen Defects at Reducible Oxide Surfaces: The Example of Ceria and Vanadia

Ganduglia‐Pirovano

2015

Defects at Oxide Surfaces

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Cerium and vanadium oxide-based systems play a major role in a variety of technological applications, with the reducibility of the systems being crucial to their functionality in the applications. The in-depth understanding and control of the type, density, and distribution of oxygen vacancies provide a means to influence the electronic structure and to tailor the systems' functionality. Hence, a great deal of experimental and theoretical work has been devoted to the study of partially reduced ceria and vanadia, both surfaces and bulk. Here, theoretical data for structural and electronic properties and energetic quantities related to the formation and interaction of neutral oxygen vacancies at the CeO 2 (111) and V 2 O 5 (001) surfaces are reviewed, discussed and compared. Experimental findings on oxygen defects in ceria and vanadia are briefly reported. Special attention is given to the fate of the electrons left in the system upon vacancy formation, the vacancy-induced lattice relaxation, whether vacancies agglomerate or repel each other, and the ability of state-of-the-art quantum-mechanical methods to provide an accurate decription of the geometric and electronic structures of the partially reduced oxide systems as well as reliable oxygen defect formation energies. IntroductionReducible metal oxides are extremely functional solid state compounds exhibiting a rich chemistry related to changes of the metal oxidation state [1]. As complex materials such as surfaces, supported particles and films, porous networks, they play a predominant role in applications in advanced technologies like catalysis, sensors, fuel cells, and microelectronics. Point defects in oxides such as vacancies and interstitials account for the transport properties of ionic solids. Defect sites on oxide supports of metal catalyst particles not only act as anchoring and nucleation centers

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Optical Absorption near the Absorption Edge in V₂O₅ Single Crystals

Cited by 33 publications

References 3 publications

On the optical properties of vanadium pentoxide single crystals

On the optical properties of vanadium pentoxide single crystals

Stability of reducedV2O5(001)surfaces

Oxygen Defects at Reducible Oxide Surfaces: The Example of Ceria and Vanadia

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Optical Absorption near the Absorption Edge in V2O5 Single Crystals

Cited by 33 publications

References 3 publications

On the optical properties of vanadium pentoxide single crystals

On the optical properties of vanadium pentoxide single crystals

Stability of reducedV2O5(001)surfaces

Oxygen Defects at Reducible Oxide Surfaces: The Example of Ceria and Vanadia

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Product

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Optical Absorption near the Absorption Edge in V₂O₅ Single Crystals