Adsorption of isolated Cu, Ni and Pd atoms on various sites of MgO(001): Density functional studies

Neyman, Konstantin M.; Vent, S.; Pacchioni, Gianfranco; Rösch, Notker

doi:10.1007/bf03185370

Cited by 48 publications

(26 citation statements)

References 19 publications

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“…In particular, we note that the monomer diffusion energy on the terrace is given as E d = 0.34 eV as against 0.23 eV [15], close to the upper limit value deduced from experiment [6].…”

Section: Embedded Clusters and Periodic Slabs: Small Pd And Ag Particsupporting

confidence: 84%

Nucleation and growth on defect sites: experiment–theory comparison for Pd/MgO(001)

Venables¹,

Giordano²,

Harding³

2006

J. Phys.: Condens. Matter

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It is well established that nucleation of metal clusters on oxide and halide surfaces is typically dominated by defect sites. Rate equation models of defect nucleation have been developed and applied to these systems. By comparing the models with nucleation density experiments, energies for defect trapping, adsorption, surface diffusion and pair binding have been deduced in favourable cases, notably for Pd deposited on Ar-cleaved MgO(001). However, the defects responsible remain largely unknown. More recently, several types of ab-initio calculation have been presented of these energies for Pd and related metals on MgO(001) containing several types of surface defects; these calculated values are surveyed, and some are widely divergent. New rate equation nucleation density predictions are presented using the calculated values. Some calculations, for some defect types, are much closer to experiment than others; the singly charged F s + centre and the neutral divacancy emerge as candidate defects. In these two cases, the Pd/MgO(001) nucleation density predictions agree well with experiment, and the corresponding surface defects deserve to be taken seriously. Energy and entropy values are discussed in the light of differences in calculated charge redistribution between the metal atoms, clusters and (charged) surface defects, and (assumed or calculated) cluster geometries.

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“…In particular, we note that the monomer diffusion energy on the terrace is given as E d = 0.34 eV as against 0.23 eV [15], close to the upper limit value deduced from experiment [6].…”

Section: Embedded Clusters and Periodic Slabs: Small Pd And Ag Particsupporting

confidence: 84%

Nucleation and growth on defect sites: experiment–theory comparison for Pd/MgO(001)

Venables¹,

Giordano²,

Harding³

2006

J. Phys.: Condens. Matter

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“…This is also consistent with the fact that the binding energy of Pd atoms on top of the O anions is not very high, 1-1.5 eV. The diffusion of the Pd atoms through the O-O channels on the surface can imply barriers of 0.5 eV or less [44], suggesting that the Pd atoms are likely to diffuse on the surface until they become trapped by some active defect. The neutral F-centers are very good candidates from this point of view since the binding of Pd to these centers is of the order of 3.5 eV.…”

Section: Adsorption Properties Of Co On Pd Atomssupporting

confidence: 83%

Synthesis of monodispersed model catalysts using softlanding cluster deposition

Abbet

Judai

Klinger

et al. 2002

Pure and Applied Chemistry

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In nanocatalysis, clusters deposited on solid, well-defined surfaces play an important role. For the detection of size effects it is, however, important to prepare samples consisting of deposited clusters of a single size, as their chemical properties change with the exact number of atoms in the cluster. In this paper, the experimental tools are presented to prepare such model systems. The existence of monodispersed clusters is confirmed by various experimental findings. First, the carbonyl formation of deposited Ni n clusters shows no change in the nuclearity when comparing the size of the deposited clusters with one of the formed carbonyls. Second, scanning tunneling microscopy (STM) studies show that fragmentation of Si n clusters upon deposition can be excluded. In addition, the adsorption behavior of CO on deposited Pd atoms points to the existence of single atoms on the surface. Furthermore, CO oxidation results on Au n clusters confirm the existence of monodispersed clusters trapped on well-defined adsorption sites. Finally, we use Monte-Carlo simulations to define the range of clusters and defect densities, for which monodispersed clusters can be expected.

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“…This paper extends previous systematic cluster model studies on the deposition of metal species at oxide substrates. [36][37][38][39][40][41] The adsorption of Pd atoms on the regular O 2Ϫ sites is an example with essentially no adsorbate-substrate charge transfer; therefore, only minor effects of the adsorption-induced lattice relaxation are expected. In the case of the charged defects F s ϩ and F s 2ϩ , the Coulomb field of the vacancy provides a driving force for distorting the structure of both the cluster and its environment.…”

Section: Introductionmentioning

confidence: 99%

Cluster embedding in an elastic polarizable environment: Density functional study of Pd atoms adsorbed at oxygen vacancies of MgO(001)

Наслузов¹,

Rivanenkov²,

Gordienko³

et al. 2001

The Journal of Chemical Physics

118

132

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Adsorption complexes of palladium atoms on F s , F s ϩ , F s 2ϩ , and O 2Ϫ centers of MgO͑001͒ surface have been investigated with a gradient-corrected ͑Becke-Perdew͒ density functional method applied to embedded cluster models. This study presents the first application of a self-consistent hybrid quantum mechanical/molecular mechanical embedding approach where the defect-induced distortions are treated variationally and the environment is allowed to react on perturbations of a reference configuration describing the regular surface. The cluster models are embedded in an elastic polarizable environment which is described at the atomistic level using a shell model treatment of ionic polarizabilities. The frontier region that separates the quantum mechanical cluster and the classical environment is represented by pseudopotential centers without basis functions. Accounting in this way for the relaxation of the electronic structure of the adsorption complex results in energy corrections of 1.9 and 5.3 eV for electron affinities of the charged defects F s ϩ and F s 2ϩ , respectively, as compared to models with a bulk-terminated geometry. The relaxation increases the stability of the adsorption complex Pd/F s by 0.4 eV and decreases the stability of the complex Pd/F s 2ϩ by 1.0 eV, but it only weakly affects the binding energy of Pd/F s ϩ . The calculations provide no indication that the metal species is oxidized, not even for the most electron deficient complex Pd/F s 2ϩ . The binding energy of the complex Pd/O 2Ϫ is calculated at Ϫ1.4 eV, that of the complex Pd/F s 2ϩ at Ϫ1.3 eV. The complexes Pd/F s and Pd/F s ϩ exhibit notably higher binding energies, Ϫ2.5 and Ϫ4.0 eV, respectively; in these complexes, a covalent polar adsorption bond is formed, accompanied by donation of electronic density to the Pd 5s orbital.

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Adsorption of isolated Cu, Ni and Pd atoms on various sites of MgO(001): Density functional studies

Cited by 48 publications

References 19 publications

Nucleation and growth on defect sites: experiment–theory comparison for Pd/MgO(001)

Nucleation and growth on defect sites: experiment–theory comparison for Pd/MgO(001)

Synthesis of monodispersed model catalysts using softlanding cluster deposition

Cluster embedding in an elastic polarizable environment: Density functional study of Pd atoms adsorbed at oxygen vacancies of MgO(001)

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