Structure of Metallic Surfaces

Certain things are easy to define, and we have already met a few other things are more easily recognised than defined. Someone once remarked / cannot define an elephant, but I m sure if I saw one I should recognise it. If is much fhe same with surfaces. It is simple to say that the surface of a solid is the interface between the bulk and the surrounding fluid phase or vacuum it is also straightforward, if somewhat more complicated, to assign thermodynamic properties to the surface phase . It is however when one starts to examine a metal surface at atomic resolution that the problems start. 

A plane occupied by atoms or ions within a crystal, or at its surface, is defined by its Miller index, which consists of integers that are the reciprocals of the intersections of that plane with the system of axes appropriate to the crystal 

Even when surface atoms have found their stable places, they will oscillate about their mean positions with a frequency which increases with temperature thus the signals given by techniques such as LEED, EXAFS and Mossbauer 

These concepts may be quantified as follows. A quantum of lattice vibration is termed a phonon, and the mean deviation of an atom from its lattice position is the mean-square displacement (u ). Phonons are detected by vibrational spectroscopy by absorption peaks below 500 cm . According to the Debye model, atoms vibrate as harmonic oscillators with a distribution of frequencies, the highest of which is COD- then the Debye temperature 9d is defined as 

The relative surface energies of different crystal planes determine the equilibrium shape of a metal crystal, and this can be predicted from knowledge of the energy terms by use of the Wulff construction.In this procedure the surface energies are drawn as vectors normal to the planes described by the indices, and these planes set at the tops of the vectors define the crystal shape. 

---

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. 

---