Computer Modeling of the Active-Site Configurations within the NO Decomposition Catalyst Cu-ZSM-5

Sayle, Dean C.; Catlow, C. Richard A.; Gale, Julian D.; Perrin, Marc A.; Nortier, Patrice

doi:10.1021/jp963459h

Cited by 47 publications

(42 citation statements)

References 26 publications

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“…33 Mackrodt and co-workers 34 have shown that this surface relaxation is an essential prerequisite in the prediction of correct morphologies for other oxide systems, namely, R-Al 2 O 3 and R-Fe 2 O 3 . Similar methods have been used to explore the crystal morphologies of other inorganic solids such as calcites, 35 zeolites, 36 and perovskite oxides, 37 where the calculated morphologies agree well with observation.…”

Section: Atomistic Simulation Methodsmentioning

confidence: 68%

Defect Chemistry, Surface Structures, and Lithium Insertion in Anatase TiO₂

2006

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Atomistic simulation techniques are used to investigate the defect properties of anatase TiO 2 and Li x TiO 2 both in the bulk and at the surfaces. Interatomic potential parameters are derived that reproduce the lattice constants of anatase, and the energies of bulk defects and surface structures are calculated. Reduction of anatase involving interstitial Ti is found to be the most favorable defect reaction in the bulk, with a lower energy than either Frenkel or Schottky reactions. The binding energies of selected defect clusters are also presented: for the Ti 3+ -Li + defect cluster, the binding energy is found to be approximately 0.5 eV, suggesting that intercalated Li ions stabilize conduction band electrons. The Li ion migration path is found to run between octahedral sites, with an activation energy of 0.45-0.65 eV for mole fractions of lithium in Li x TiO 2 of x e 0.1. The calculated surface energies are used to predict the crystal morphology, which is found to be a truncated bipyramid in which only the (101) and (001) surfaces are expressed, in accord with the available microscopy data. Calculations of defect energies at the (101) surface suggest that single Ti 3+ defects and neutral Ti 3+ -Li + pairs tend to segregate to the surface.

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Section: Atomistic Simulation Methodsmentioning

confidence: 68%

Defect Chemistry, Surface Structures, and Lithium Insertion in Anatase TiO₂

2006

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“…Such effects cannot be described by radial interactions, but rather require the introduction of angular forces describing the energetics of the transition-metal d-shell. Most existing methods for including angular forces in simulations of metal ions have used assumed functional forms (Comba et al, 1995, Allured et al, 1991, Timofeeva et al, 1995, Wiesemann et al, 1994, Sayle et al, 1995, Sayle et al, 1997 based, for example on the observed structures of small complexes. A recently developed method (Landis et al, 1998) treats the environment-dependent energetics of transition metals via a valence-bond approach.…”

Section: Introductionmentioning

confidence: 99%

The Functional Form of Angular Forces around Transition Metal Ions in Biomolecules

Carlsson

Zapata

2001

Biophysical Journal

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A method for generating angular forces around sigma-bonded transition metal ions is generalized to treat pi-bonded configurations. The theoretical approach is based on an analysis of ligand-field and small-cluster Hamiltonians based on the moments of the electron state distribution. The functional forms that are obtained involve a modification of the usual expression of the binding energy as a sum of ligand-ligand interactions, which, however, requires very little increase in CPU time. The angular interactions have simple forms involving sin and cos functions, whose relative weights depend on whether the ligands are sigma- or pi-bonded. They describe the ligand-field stabilization energy to an accuracy of about 10%, and the interaction energy of covalently bonded systems to an accuracy of better than 4%. The resulting functional forms for the force field are used to model the structure of small clusters, including fragments of the copper blue protein structure. Large deviations from the typical square copper coordination are found when pi-bonded ligands are present.

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“…For this purpose extended models should have been considered, which would include larger parts of the framework indispensable to distinguish between structural fragments, large enough to be less sensitive to saturation scheme. Such approach has already been pursued by many authors, within both semiclassical [17] and more rigorous quantum chemical regime [18][19][20][21]. On the basis of previous experience of other researchers [20,21] and our own studies the following model has been proposed for the α position in ZSM-5 after careful probing several possibilities.…”

Section: Methodological Remarksmentioning

confidence: 99%