Structure of metal surfaces

At present the detailed knowledge of the outermost layers of a clean metal surface is based on electron spectroscopy or scattering of neutral atoms. Low-energy electron diffraction (LEED) and helium (for instance) scattering give structural information about the top of the surface in ultrahigh vacuum (UHV). Are the surfaces observed in UHV close to the models described in Section III.4  

In some cases they are, but for platinum, iridium, and gold a reconstruction of the first outermost layer of atoms was observed for some faces of simple indices. Of these three metals, only gold is within the scope of this chapter. Numerous papers were written about the surface reconstruction of gold which, however, happens only under certain conditions of cleanliness and temperature. 

It is conventional to describe the real surface by a notation which compares it with the ideal one. The surface net is indexed with respect to the bulk net as a p x g unit cell. A top layer, which is just a bulk termination, is denoted 1x1. 

The Au(lOO) face surface is approximated by a 20 x 5 (or 1x5) unit cell this implies a bond-length reduction of a few percent. Then there is a mismatch between the topmost layer and the substrate (the bulk) that would increase the strain energy at the surface. A buckling of the surface is accepted as an explanation of 

The Au(lll) face, which is the closest packed fee structure, is known to have the lowest surface energy among all possible fee crystal faces. The clean Au( 111) face surface was first approximated to be a /3 X /3.R30° unit cell. A model with a uniaxially contracted top hexagonal layer was proposed and a charge-density-wave (CDW) structure was also proposed as an explanation of the LEED observations.  

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Almost all that is known about the crystal face specificity of double-layer parameters has been obtained from studies with metal single-crystal faces in aqueous solutions. Studies in nonaqueous solvents would be welcome to obtain a better understanding of the influence of the crystallographic structure of metal surfaces on the orientation of solvent molecules at the interface in relation to their molecular properties. 

Surface-enhanced Raman scattering (SERS) is a candidates for resolving this issue. Since the SERS effect is observed only at metal surfaces with nanosized curvature, this technique can also be used to investigate nanoscale morphological structures of metal surfaces. It is thus worth investigating SERS under oscillatory electrodeposition conditions. The author of this chapter and coworkers recently reported that... 

The above studies show that the chemisorptions on metals could often alter the composition and structure of metal surfaces. To bridge the pressure gap, in situ STM has played a critical role in observing the dynamic behavior of catalytic surfaces from UHV to atmospheric pressures. 

Lang, N. D. (1973). The density-functional formalism and the electronic structure of metal surfaces. In Solid State Physics, edited by H. Ehrenreich, F. Seitz, and D. Turnbull, Vol. 28, Academic, New York. 

RECENT DEVELOPMENTS IN THE ELECTRONIC STRUCTURE OF METAL SURFACES... 

Much has been learned in recent years about the structures of metal surfaces. which do not always parallel the crystallography of the bulk material. Well dehned single-crystal surfaces provide us with an atomic view that is helpful in deciphering similar structures existing on dispersed metals. ... 

Structures of Metal Surfaces and Their Effects on Electrocatalysis... 

Heidenreich, R. D.,and V. G. Peck Fine structure of metallic surfaces with... 

At the atomic scale, the structure of metal surfaces depends on the crystal orientation and on the presence of crystalline defects. We shall distinguish three kinds of surfaces ... 

Daniel C, Miicklich F, Liu Z. (2003) Periodical micto-nano-structuring of metallic surfaces by interfering laser beams. App SurfSci 208-209 317-321. 

In this communication I will compare the electronic structures of metal surfaces with that of metalloporphyrins and discuss the possibility of isolate non-local electronic perturbations for CO terminally bound to metal surfaces from the vibrational spectra of carbonyl-hemes. 

This section is dedicated to the main focus of the UHV experiments in this thesis, the electronic structure of metal surfaces, supported metal clusters and adsorbate interactions. In the light of the idea to tune reactivity by the modification of the catalyst (i.e. size) a brief introduction of adsorption and the electronic stmcture of the catalyst adsorbate interaction is given Further, an overview over EES results on metal particles and clusters is presented, followed by a sections about EES of adsorbates and the data treatment for comparison to gas phase spectra, applied in this work. 

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