Alloys, surface structure

RECONSTRUCTED CLEAN METALS AND ALLOY SURFACE STRUCTURES... 

TABLE 2,3b. Reconstructed Clean Metals and Alloy Surface Structures... 

Before any attempt to establish a correlation between the surface structure of the oxidized alloys and their CO conversion activity one must stress that the surface composition of the samples under reaction conditions may not necessarily be Identical to that determined from ESCA data. Moreover, surface nickel content estimates from ESCA relative Intensity measurements are at best seml-quantlta-tlve. This can be readily rationalized If one takes Into consideration ESCA finite escape depth, the dependence of ESCA Intensity ratio... 

Kuntze J, Speller S, Heiland W, Atrei A, Rovida G, Bardi U. 1999. Surface structure and composition of the alloy Au3Pd(100) determined by LEED and ion scattering spectroscopy. Phys Rev B 60 1535-1538. 

TABLE 9.3 The Electronic Structure of the Pt and PtsCo Alloy Surfaces. Reprinted with Permission from Xu et al. [2004]... 

DFT calculations show that, like PtsCo alloy surfaces, the electronic structure of the Pd skin is modified by strain and the underlying alloy, which in turn modifies the... 

In summary, the alumina nanolayers formed by the high-temperature oxidation on NiAl alloy surfaces are structurally and chemically very different from the bulk-terminated surfaces of the various A1203 phases, and they thus provide very prototypical examples of oxide phases with novel emergent properties because of interfacial bonding and thickness confinement effects. 

Mono- or single-crystal materials are undoubtedly the most straightforward to handle conceptually, however, and we start our consideration of electrochemistry by examining some simple substances to show how the surface structure follows immediately from the bulk structure we will need this information in chapter 2, since modern single-crystal studies have shed considerable light on the mechanism of many prototypical electrochemical reactions. The great majority of electrode materials are either elemental metals or metal alloys, most of which have a face-centred or body-centred cubic structure, or one based on a hexagonal close-packed array of atoms. 

Surface alloys, micro structure of, 14 451 Surface analysis, 10 428... 

Turek, I., Drchal, V., Kudrnovsky, J., Sob, M. and Weinberger, P. (1996), Electronic Structure of Disordered Alloys, Surfaces and Interfaces, Kluwer, Boston. 

The EAM has been used to study the surface structure of other metals and metal alloys. For example. Daw has suggested that a missing row configuration is also the likely structure for the (2 x 1) reconstruction of the Pt(l 10) surface. Studies have also been made of the surface structures of various alloys, where for example surface segregation of one constituent over the other has been observed ° . In addition to studies of specific systems, the EAM formalism is also sufficiently general that it has been used to understand trends in surface reconstructions among various metals . ... 

The combined use of the modem tools of surface science should allow one to understand many fundamental questions in catalysis, at least for metals. These tools afford the experimentalist with an abundance of information on surface structure, surface composition, surface electronic structure, reaction mechanism, and reaction rate parameters for elementary steps. In combination they yield direct information on the effects of surface structure and composition on heterogeneous reactivity or, more accurately, surface reactivity. Consequently, the origin of well-known effects in catalysis such as structure sensitivity, selective poisoning, ligand and ensemble effects in alloy catalysis, catalytic promotion, chemical specificity, volcano effects, to name just a few, should be subject to study via surface science. In addition, mechanistic and kinetic studies can yield information helpful in unraveling results obtained in flow reactors under greatly different operating conditions. 

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