Cluster modeling of metal oxides: how to cut out a cluster?

Lü, Xin; Xu, Xin; Wang, Nanqin; Zhang, Qianer; Ehara, Masahiro; Nakatsuji, Hiroshi

doi:10.1016/s0009-2614(98)00611-3

Cited by 55 publications

(12 citation statements)

References 26 publications

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“…The cluster models implemented here conform to the three principles proposed to model metal oxides using clusters. 34,35 These principles are the neutrality principle, the stoichiometry principle and the coordination principle. The electronic structure descriptors such as density of states and orbital analysis were calculated using the software package AOMix.…”

Section: Computational Detailsmentioning

confidence: 99%

Oxygen adsorption onto pure and doped Al surfaces – the role of surface dopants

Lousada

Korzhavyi

2015

Phys. Chem. Chem. Phys.

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Using density functional theory (DFT) with the PBE0 density functional we investigated the role of surface dopants in the molecular and dissociative adsorption of O2 onto Al clusters of types Al50, Al50Alad, Al50X and Al49X, where X represents a dopant atom of the following elements Si, Mg, Cu, Sc, Zr, and Ti. Each dopant atom was placed on the Al(111) surface as an adatom or as a substitutional atom, in the last case replacing a surface Al atom. We found that for the same dopant geometry, the closer is the ionization energy of the dopant element to that of elemental Al, the more exothermic is the dissociative adsorption of O2 and the stronger are the bonds between the resulting O atoms and the surface. Additionally we show that the Mulliken concept of electronegativity can be applied in the prediction of the dissociative adsorption energy of O2 on the doped surfaces. The Mulliken modified second-stage electronegativity of the dopant atom is proportional to the exothermicity of the dissociative adsorption of O2. For the same dopant element in an adatom position the dissociation of O2 is more exothermic when compared to the case where the dopant occupies a substitutional position. These observations are discussed in view of the overlap population densities of states (OPDOS) computed as the overlap between the electronic states of the adsorbate O atoms and the clusters. It is shown that a more covalent character in the bonding between the Al surface and the dopant atom causes a more exothermic dissociation of O2 and stronger bonding with the O atoms when compared to a more ionic character in the bonding between the dopant and the Al surface. The extent of the adsorption site reconstruction is dopant atom dependent and is an important parameter for determining the mode of adsorption, adsorption energy and electronic structure of the product of O2 adsorption. The PBE0 functional could predict the existence of the O2 molecular adsorption product for many of the cases investigated here.

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Section: Computational Detailsmentioning

confidence: 99%

Oxygen adsorption onto pure and doped Al surfaces – the role of surface dopants

Lousada

Korzhavyi

2015

Phys. Chem. Chem. Phys.

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“…In general, the sub-nanometric cluster is very unstable, because a large quantity of coordinatively unsaturated sites exist in the outer layer. 39,40 The requirement to saturate these coordinatively unsaturated sites provides a tremendous driving force for stabilizing the subnanometric ZnO clusters in zeolite channels or cavities. In the case of ZnO/HY materials, the coordinatively unsaturated zinc sites of the ZnO cluster encapsulated inside the supercage strongly interact with the framework oxygen atoms.…”

Section: Zno Clusters In Zeolites Characterized By Uv-visiblementioning

confidence: 99%

ZnO Clusters Encapsulated inside Micropores of Zeolites Studied by UV Raman and Laser-Induced Luminescence Spectroscopies

et al. 2004

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Using microporous zeolites as host, sub-nanometric ZnO clusters were prepared in the micropores of the host by the incipient wetness impregnation method. A small amount of sub-nanometric ZnO clusters were introduced into the channels of HZSM-5 zeolite, whereas a large quantity of sub-nanometric ZnO clusters can be accommodated in the supercages of HY zeolite and no macrocrystalline ZnO exists on the extra surface of the HY material. The vibrations of the zeolite framework and ZnO were characterized by UV Raman spectroscopy. The optical properties of these ZnO clusters were studied by UV-visible absorption spectroscopy and laser-induced luminescence spectroscopy. It is found that there are strong host-guest interactions between the framework oxygen atoms of zeolite and ZnO clusters influencing the motions of the framework oxygen atoms. The interaction may be the reason why ZnO clusters are stabilized in the pores of zeolites. Different from bulk ZnO materials, these sub-nanometric ZnO clusters exhibit their absorption onset below 265 nm and show a purple luminescence band (centered at 410-445 nm) that possesses high quantum efficiency and quantum size effect. This purple luminescence band most likely originates from the coordinatively unsaturated Zn sites in sub-nanometric ZnO clusters. On the other hand, the differences in the pore structure between HZSM-5 and HY zeolites cause the absorption edge and the purple luminescence band of ZnO clusters in ZnO/HZSM-5 show a red shift in comparison with those of ZnO clusters in ZnO/HY.

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“…One approach to creating structural models of clusters is to maintain stoichiometry, preserve neutrality and limit the number of dangling bonds [7]. This approach is validated with recent theoretical studies on very small clusters showing that charge and excess oxygen lead to instability [8].…”

Section: Introductionmentioning

confidence: 88%

Structural Features That Stabilize ZnO Clusters: An Electronic Structure Approach

Szakacs

Poduska

2013

Computation

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We show that a simple approach to building small computationally inexpensive clusters offers insights on specific structural motifs that stabilize the electronic structure of ZnO. All-electron calculations on Zn i O i needle (i = 6, 9, 12, 15, and 18) and plate (i = 9 and 18) clusters within the density functional theory (DFT) formalism show a higher stability for ZnO needles that increases with length. Puckering of the rings to achieve a more wurtzite-like structure destabilizes the needles, although this destabilization is reduced by going to infinite needles (calculated using periodic boundary conditions). Calculations of density of states (DOS) curves and band gaps for finite clusters and infinite needles highlight opportunities for band-gap tuning through kinetic control of nanocrystal growth.

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Cluster modeling of metal oxides: how to cut out a cluster?

Cited by 55 publications

References 26 publications

Oxygen adsorption onto pure and doped Al surfaces – the role of surface dopants

Oxygen adsorption onto pure and doped Al surfaces – the role of surface dopants

ZnO Clusters Encapsulated inside Micropores of Zeolites Studied by UV Raman and Laser-Induced Luminescence Spectroscopies

Structural Features That Stabilize ZnO Clusters: An Electronic Structure Approach

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