Highly under-coordinated atoms at Rh surfaces: interplay of strain and coordination effects on core level shift

Baraldi, Alessandro; Bianchettin, Laura; Vesselli, Erik; Gironcoli, Stefano de; Lizzit, Silvano; Petaccia, L.; Zampieri, G.; Comelli, Giovanni; Rosei, R.

doi:10.1088/1367-2630/9/5/143

Cited by 52 publications

(66 citation statements)

References 51 publications

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“…Finally, the comparison with the results of single adatoms and dimers deposited on {111} and {100} Rh surfaces 40 suggests that the third component, Rh E , should be assigned to under-coordinated Rh atoms at the edges of the clusters, as will be confirmed later by DFT calculations. Oxygen contamination, both in terms of chemisorbed atoms or oxidic species, has the effect of increasing the Rh 3d 5/2 BE on Rh atoms.…”

Section: Articlementioning

confidence: 52%

“…To highlight the link between the local geometric configuration and the corresponding electronic structure, we have plotted the core level shift data for all of the different atomic configurations as a function of their effective coordination number C E , 40 which takes into account both the effects of the coordination number C N and of the local bond strain, that is, the changes of the RhÀRh average distance. This definition naturally assigns larger contributions to closer atoms and smoothly phases out farther ones.…”

Section: Articlementioning

confidence: 99%

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Local Electronic Structure and Density of Edge and Facet Atoms at Rh Nanoclusters Self-Assembled on a Graphene Template

et al. 2012

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T he interest in developing novel materials using building blocks with sizes of about 1 nm has motivated the huge effort devoted to understand the properties of nanoclusters. Several studies have clearly demonstrated that atomic aggregates in the nanometer size range, that is, formed by dozens or hundreds of atoms, present remarkably different properties with respect to their bulk crystalline counterparts. Heterogeneous catalysis, energy conversion, and magnetic data storage are among the technologically most relevant fields where supported nanoclusters are expected to have a strong impact. 1,2 An important field for application of the new nanocluster-based materials is catalysis. The most striking example is the high chemical activity of small Au nanoclusters, 3À6 given by highly reactive corner and edge atoms with low coordination number C N , but even other transition metals like Pt present nanoclusters with a similar behavior. 7,8 One of the goals of nanotechnology is the manipulation of the magnetic properties in systems with reduced dimensionality, such as quantum wires, quantum dots, and nanoclusters. As an example, the use of nanoclusters for ultrahigh density magnetic recording requires pushing further away the superparamagnetic limit by enhancing the magnetic anisotropy energy. In this respect, experiments have shown that low C N atoms play a pivotal role. 9,10 When the particle's size is reduced to only 10À20 Å, two main challenges are posed: (i) the formation in a controllable and reproducible manner of large-scale replicas of these individual building blocks on a suitable substrate 11 and (ii) the determination and tuning of the geometric and electronic structure of the supported nanoobjects.One of the most recent solutions to meet the first challenge is to make use of template graphene (GR) for the growth of metallic nanoclusters and for the formation of long-range-ordered superstructures. This * Address correspondence to alessandro.baraldi@elettra.trieste.it.Received for review November 24, 2011 and accepted March 9, 2012. Published online 10.1021/nn300651s ABSTRACTThe chemical and physical properties of nanoclusters largely depend on their sizes and shapes. This is partly due to finite size effects influencing the local electronic structure of the nanocluster atoms which are located on the nanofacets and on their edges. Here we present a thorough study on graphene-supported Rh nanocluster assemblies and their geometrydependent electronic structure obtained by combining high-energy resolution core level photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory. We demonstrate the possibility to finely control the morphology and the degree of structural order of Rh clusters grown in register with the template surface of graphene/Ir(111). By comparing measured and calculated core electron binding energies, we identify edge, facet, and bulk atoms of the nanoclusters. We describe how small interatomic distance changes occur while varying the nanocluster size, substantia...

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Section: Articlementioning

confidence: 52%

Section: Articlementioning

confidence: 99%

Local Electronic Structure and Density of Edge and Facet Atoms at Rh Nanoclusters Self-Assembled on a Graphene Template

et al. 2012

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“…8 Recently it has been shown that this parameter can be used to rationalize trends in surface core level shifts when undercoordinated Rh atoms assume a variety of geometries. 9 In the present case, the effective coordination of surface atoms is progressively lowered as one proceeds from system ͑i͒ to system ͑iv͒, as we will show further below.…”

Section: Introductionmentioning

confidence: 58%

Effective coordination as a predictor of adsorption energies: A model study of NO on Rh(100) and Rh/MgO(100) surfaces

et al. 2009

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We have studied the adsorption of NO, and the coadsorption of N and O, on four physical and hypothetical systems: unstrained and strained Rh͑100͒ surfaces and monolayers of Rh atoms on strained and unstrained MgO͑100͒ surfaces. We find that as we go from Rh͑100͒ to Rh/Mg0͑100͒, via the other two hypothetical systems, the effective coordination progressively decreases, the d band narrows and its center shifts closer to the Fermi level, and the strength of adsorption and coadsorption increases. Both the strain and the presence of the oxide substrate contribute significantly to this. However, charge transfer is found to play a negligible role due to a canceling out between donation and back-donation processes. Our results suggest that lowering the effective coordination of Rh catalysts by strain, roughening, or the use of inert substrates might lower activation energies for the dissociation of NO.

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“…various registries of Pd [9], Rh [46], and Ag [47] skins [45,48] . A slight deviation in the slopes arises from the accuracy in measurements.…”

Section: Nanosolid Clsmentioning

confidence: 99%

Electrons: Entrapment and Polarization

Sun

2014

Springer Series in Chemical Physics

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Highly under-coordinated atoms at Rh surfaces: interplay of strain and coordination effects on core level shift

Cited by 52 publications

References 51 publications

Local Electronic Structure and Density of Edge and Facet Atoms at Rh Nanoclusters Self-Assembled on a Graphene Template

Local Electronic Structure and Density of Edge and Facet Atoms at Rh Nanoclusters Self-Assembled on a Graphene Template

Effective coordination as a predictor of adsorption energies: A model study of NO on Rh(100) and Rh/MgO(100) surfaces

Electrons: Entrapment and Polarization

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