Electronic structure of reduced titanium dioxide

Paxton, Anthony; Thiên-Nga, L.

doi:10.1103/physrevb.57.1579

Cited by 154 publications

(128 citation statements)

References 15 publications

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“…Explicit treatment of the semicore Ti ͑3s, 3 p͒ states as valence orbitals was found to be important as has previously been shown in studies of the structure of bulk rutile. 21 Moreover, as is demonstrated in Sec. VIII, the shift of the semicore Ti levels depends on the insertion concentration.…”

Section: Details Of the Simulationssupporting

confidence: 48%

Density-functional simulations of lithium intercalation in rutile

2002

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Density-functional simulations of lithium intercalation into rutile structured titanium dioxide are presented. Full relaxation of structures for a wide range of insertion concentrations is used to identify the thermodynamically most stable configurations and Li-ion site preferences. The host lattice is found to undergo large deformations upon Li insertion, which can be related to the excitation of soft vibrational modes. The dominant screening interaction is found to be due to these elastic distortions of the lattice rather than to dielectric screening. This leads to highly anisotropic and concentration-dependent effective Li-Li interactions, which are not easily amenable to empirical parametrization. The anisotropic volume expansion is found to be largely due to the increase in the radii of reduced Ti ions as they accommodate charge donated to the lattice. The computed open circuit voltage ͑OCV͒ reproduces the characteristic features of experimental discharge curves at elevated temperature. The computed Li-ion energy surfaces reveal highly anisotropic diffusion. A model of Li intercalation is proposed, which takes account of both the thermodynamic and kinetic properties computed here. This model is used to resolve apparent contradictions in the current interpretation of the measured OCV and its dependence on temperature. Predicted changes in the electronic structure and their relationship to the interaction between structural, charge, and spin degrees of freedom are discussed in detail.

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Section: Details Of the Simulationssupporting

confidence: 48%

Density-functional simulations of lithium intercalation in rutile

2002

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“…Recent all-electron DFT-LDA calculations for the oxygen deficient surface find Ti 3d states at the bottom of the conduction band and hence a conducting surface layer. 33 This is not unexpected as DFT tends to underestimate band gaps. In order to examine the effect of exchange and correlation approximations on the nature of the surface electronic structure of the K-adsorbed surface, we have relaxed the surface structure and computed the electronic structure using DFT-LDA.…”

Section: B the Nature Of The Electronic Statementioning

confidence: 86%

“…14,7,28 Spin-polarized states at a similar energy with respect to the VBM were found in recent theoretical investigations of potassium adsorption on the ͑110͒ surface 52 and on oxygen deficient ͑110͒ surfaces in which both DFT and HF approaches were used. 17,16,33 Although all of these approaches obtain a similar description of the occupied eigenvalue spectrum they give significantly different descriptions of the separation between the localized states and the conduction band minimum ͑CBM͒. The spectroscopy measurements in the literature do not determine accurately the size of this separation but there is some evidence that a small gap does exist.…”

Section: B the Nature Of The Electronic Statementioning

confidence: 93%

“…We have used HF theory ͑which has been shown in recent work to provide an accurate description of the ground state energetics and electronic structure of transition metal insulators 17,32 ͒ to examine the K adsorption process in order to better understand the nature of the charge transfer state and its consequences for the geometry and electronic structure. Supplementary calculations were performed using DFT within the local density approximation ͑LDA͒ to facilitate comparisons with previous DFT studies 16,33 of reduced TiO 2 surfaces.…”

Section: Introductionmentioning

confidence: 99%

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First-principles study of potassium adsorption onTiO2surfaces

1999

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We present an ab initio study of alkali metal adsorption on metal oxide surfaces. We have investigated the changes that occur to the structure and electronic properties of the rutile TiO 2 ͑100͒ surface when a 1 2 monolayer of potassium atoms is adsorbed. The K atoms are reduced to K ϩ ions as charge transfer occurs from the K 3s orbital to localized Ti 3d orbitals at the surface of the substrate. The occupied Ti 3d states lie about 1 eV above the O 2 p valence band maximum in agreement with recent photoemission studies. The Ti 3d states are spin polarized and are similar to those found at oxygen deficient TiO 2 surfaces. The geometric structure also undergoes significant relaxation as the lattice is polarized around the reduced Ti sites. The calculated surface structure is in excellent agreement with x-ray adsorption data. ͓S0163-1829͑99͒04224-1͔

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“…The valence band of TiO 2 is composed of the 2p orbitals of oxygen hybridized with the 3d orbitals of titanium, while the conduction band is only the 3d orbitals of titanium [42]. When TiO 2 is exposed to near-UV light, electrons in the valence band are excited to the conduction band leaving behind holes (h + ), as shown in Figure 3.…”

Section: Chemical Structure Of Tiomentioning

confidence: 99%

A review of TiO2 nanoparticles

2011

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Climate change and the consumption of non-renewable resources are considered as the greatest problems facing humankind. Because of this, photocatalysis research has been rapidly expanding. TiO 2 nanoparticles have been extensively investigated for photocatalytic applications including the decomposition of organic compounds and production of H 2 as a fuel using solar energy. This article reviews the structure and electronic properties of TiO 2 , compares TiO 2 with other common semiconductors used for photocatalytic applications and clarifies the advantages of using TiO 2 nanoparticles. TiO 2 is considered close to an ideal semiconductor for photocatalysis but possesses certain limitations such as poor absorption of visible radiation and rapid recombination of photogenerated electron/hole pairs. In this review article, various methods used to enhance the photocatalytic characteristics of TiO 2 including dye sensitization, doping, coupling and capping are discussed. Environmental and energy applications of TiO 2 , including photocatalytic treatment of wastewater, pesticide degradation and water splitting to produce hydrogen have been summarized. Historical backgroundThe growth of industry worldwide has tremendously increased the generation and accumulation of waste byproducts. In general, the production of useful products has been focused on and the generation of waste byproducts has been largely ignored. This has caused severe environmental problems that have become a major concern. Researchers all over the world have been working on various approaches to address this issue. Photoinduced processes have been studied and various applications have been developed. One important technique for removing industrial waste is the use of light energy (electromagnetic radiation) and particles sensitive to this energy to mineralize waste which aids in its removal from solution. Titanium dioxide (TiO 2 ) is considered very close to an ideal semiconductor for photocatalysis because of its high stability, low cost and safety toward both humans and the environment.*Corresponding author (email: shipra.mital@gmail.com)In 1964, Kato et al.[1] published their work on the photocatalytic oxidation of tetralin (1,2,3,4-tetrahydronaphthalene) by a TiO 2 suspension, which was followed by McLintock et al. [2] investigating the photocatalytic oxidation of ethylene and propylene in the presence of oxygen adsorbed on TiO 2 . However, the most important discovery that extensively promoted the field of photocatalysis was the "Honda-Fujishima Effect" first described by Fujishima and Honda in 1972 [3]. This well-known chemical phenomenon involves electrolysis of water, which is related to photocatalysis. Photoirradiation of a TiO 2 (rutile) single crystal electrode immersed in an aqueous electrolyte solution induced the evolution of oxygen from the TiO 2 electrode and the evolution of hydrogen from a platinum counterelectrode when an anodic bias was applied to the TiO 2 working electrode. In 1977, Frank and Bard [4] examined the reduction of ...

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Electronic structure of reduced titanium dioxide

Cited by 154 publications

References 15 publications

Density-functional simulations of lithium intercalation in rutile

Density-functional simulations of lithium intercalation in rutile

First-principles study of potassium adsorption onTiO2surfaces

A review of TiO2 nanoparticles

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