Electron hole formation in acidic zeolite catalysts

Solans‐Monfort, Xavier; Branchadell, Vicenç; Sodupe, Mariona; Sierka, Marek; Sauer, Joachim

doi:10.1063/1.1781122

Cited by 50 publications

(42 citation statements)

References 75 publications

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“…This is well known in the literature 51,69 and has been observed before, e.g., with the size-induced d-electron localization in polyhedral vanadium oxide anion cages 70 and the formation of electron holes in solid oxides. 71,72 The crossover point between DFT functionals with increasing amount of exact exchange for the physically correct description of the electronic structure depends on the observed system. In the present study, standard GGA functionals, and also hybrid functional with the standard amount of Fock exchange, e.g., 20% for B3LYP, incorrectly predict the electronic structure to be delocalized and the geometric structure to be D 2h symmetric (if possible by stoichiometric composition).…”

Section: Discussionmentioning

confidence: 99%

Gas phase structures and charge localization in small aluminum oxide anions: Infrared photodissociation spectroscopy and electronic structure calculations

Song

Fagiani

Gewinner

et al. 2016

The Journal of Chemical Physics

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We use cryogenic ion trap vibrational spectroscopy in combination with quantum chemical calculations to study the structure of mono-and dialuminum oxide anions. The infrared photodissociation spectra of D 2 -tagged AlO 1-4 − and Al 2 O 3-6 − are measured in the region from 400 to 1200 cm −1 . Structures are assigned based on a comparison to simulated harmonic and anharmonic IR spectra derived from electronic structure calculations. The monoaluminum anions contain an even number of electrons and exhibit an electronic closed-shell ground state. The Al 2 O 3-6 − anions are oxygen-centered radicals. As a result of a delicate balance between localization and delocalization of the unpaired electron, only the BHLYP functional is able to qualitatively describe the observed IR spectra of all species with the exception of AlO 3 − . Terminal Al-O stretching modes are found between 1140 and 960 cm −1 . Superoxo and peroxo stretching modes are found at higher (1120-1010 cm −1 ) and lower energies (850-570 cm −1 ), respectively. Four modes in-between 910 and 530 cm −1 represent the IR fingerprint of the common structural motif of dialuminum oxide anions, an asymmetric four-member Al-(O) 2 -Al ring. Published by AIP Publishing. [http://dx

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Section: Discussionmentioning

confidence: 99%

Gas phase structures and charge localization in small aluminum oxide anions: Infrared photodissociation spectroscopy and electronic structure calculations

Song

Fagiani

Gewinner

et al. 2016

The Journal of Chemical Physics

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“…Extending systematic computer-based design beyond transition-metal catalysts provides a considerable challenge from a theoretical point of view. We know from detailed comparisons between theory and experiment that density functional theory works quite well for the transition metals, but we also know that it often works somewhat worse for other classes of potential catalysts, such as, for example, strongly correlated oxides (69)(70)(71)(72)(73).…”

Section: Challenges In Theoretical Surfacementioning

confidence: 99%

Density functional theory in surface chemistry and catalysis

Nørskov

Abild‐Pedersen

Studt

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

1,963

1,342

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Recent advances in the understanding of reactivity trends for chemistry at transition-metal surfaces have enabled in silico design of heterogeneous catalysts in a few cases. The current status of the field is discussed with an emphasis on the role of coupling theory and experiment and future challenges. S urface chemistry is interesting and challenging for several reasons. It takes place at the border between the solid state and the liquid or gas phase and can be viewed as a meeting place between condensed-matter physics and chemistry. The phenomena at the solid-gas or solid-liquid interface are complicated for this reason. A chemical reaction at a metal surface, for instance, has all of the complexity of ordinary gas-phase reactions, but in addition the usual electron conservation rules do not apply because the metal provides a semi-infinite source of electrons at the Fermi level. A new set of concepts therefore needs to be developed to describe surface chemistry.An understanding of surface chemical reactions is necessary to describe a large number of surface phenomena including semiconductor processing, corrosion, electrochemistry, and heterogeneous catalysis. Heterogeneous catalysis alone has been estimated to be a prerequisite for more than 20% of all production in the industrial world (1), and it will most likely gain further importance in the years to come. The development of sustainable energy solutions represents one of the most important scientific and technical challenges of our time, and heterogeneous catalysis is at the heart of the problem. Most sustainable energy systems rely on the energy influx from the sun. Sunlight is diffuse and intermittent, and it is therefore essential to be able to store the energy, for example chemically as a fuel or in a battery. Such storage can then provide energy for the transportation sector and in decentralized applications, as it evens out temporal variations (2, 3). The key to providing an efficient transformation of energy to a chemical form or from one chemical form into another is the availability of suitable catalysts. In essentially all possible sustainable energy technologies, the lack of efficient and economically viable catalysts is a primary factor limiting their use (3, 4).In the present paper, we will discuss the status of the development of an understanding of surface chemistry. We will do this from a theoretical perspective, but it is important to stress that it is a close coupling between theory and experiment which has enabled the developments thus far. Surface science experiments have been invaluable in providing a quantitative description of a range of surface phenomena (5-14). This has been essential in benchmarking computational surface science based on density functional theory (DFT) calculations and in providing experimental guidance and verification of the concepts developed. This forms a good background for the development of an understanding of heterogeneous catalysis, which is the other part of this paper. We will show how the concepts dev...

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“…17) have proven to fail in describing charge localization in Al-doped silica. 12,13,[18][19][20] Thus, it has been argued that a large amount of EXX would be necessary to obtain agreement with experiments, 12,19 much like a large enough Hubbard U parameter is needed within DFT+U to solve the same problem. 21 For instance, To et al found that a semi-empirical hybrid functional including 42% of EXX (called BB1K functional) yields the correct picture.…”

Section: Introductionmentioning

confidence: 99%

Communication: Hole localization in Al-doped quartz SiO2 within ab initio hybrid-functional DFT

Gerosa

Valentin

Bottani

et al. 2015

The Journal of Chemical Physics

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Articles you may be interested inDefect calculations in semiconductors through a dielectric-dependent hybrid DFT functional: The case of oxygen vacancies in metal oxides The Journal of Chemical Physics 143, 134702 (2015) We investigate the long-standing problem of hole localization at the Al impurity in quartz SiO 2 , using a relatively recent DFT hybrid-functional method in which the exchange fraction is obtained ab initio, based on an analogy with the static many-body COHSEX approximation to the electron self-energy. As the amount of the admixed exact exchange in hybrid functionals has been shown to be determinant for properly capturing the hole localization, this problem constitutes a prototypical benchmark for the accuracy of the method, allowing one to assess to what extent self-interaction effects are avoided. We obtain good results in terms of description of the charge localization and structural distortion around the Al center, improving with respect to the more popular B3LYP hybrid-functional approach.We also discuss the accuracy of computed hyperfine parameters, by comparison with previous calculations based on other self-interaction-free methods, as well as experimental values. We discuss and rationalize the limitations of our approach in computing defect-related excitation energies in lowdielectric-constant insulators. C 2015 AIP Publishing LLC.[http://dx

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Electron hole formation in acidic zeolite catalysts

Cited by 50 publications

References 75 publications

Gas phase structures and charge localization in small aluminum oxide anions: Infrared photodissociation spectroscopy and electronic structure calculations

Gas phase structures and charge localization in small aluminum oxide anions: Infrared photodissociation spectroscopy and electronic structure calculations

Density functional theory in surface chemistry and catalysis

Communication: Hole localization in Al-doped quartz SiO2 within ab initio hybrid-functional DFT

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