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Kinked surface

A kinked surface, like fee (10,8,7), can also be approximately expressed in this fomi the step plane (h k / ) is a stepped surface itself, and thus has higher Miller indices than tlie terrace plane. However, the step notation does not exactly tell us the relative location of adjacent steps, and it is not entirely clear how the terrace width M should be counted. A more complete microfacet notation is available to describe kinked surfaces generally [5]. [Pg.1762]

The Pt(lll) surface continues to show undetectable activity as the oxygen content increases, although the activity passes through a maximum for both the stepped and kinked surfaces with increasing oxygen content. [Pg.455]

Compared at their respective maxima, the kinked surface is more active than the stepped surface. [Pg.455]

The oxygen content at the maximum is slightly higher for the stepped surface than for the kinked surface. [Pg.455]

We may turn now to consider the results provided by the several sets of DFT calculations (see Appendix) that relate to massive gold surfaces.13-15,20 21,24 25 45 These treat in particular the likelihood of molecular adsorption, the activation energy for dissociative chemisorption and the strength of adsorption (binding energy) of oxygen atoms on Au(lll), Au(211) (a stepped surface), Au(221) (a kinked surface), as well... [Pg.130]

Chemisorption on supported metals is necessarily more complex than on massive metals there are a greater diversity of types of gold atom at the surface of particles, because in addition to those found on stepped or kinked surfaces, some are close to the support surface and may be influenced by it, and there is the strong possibility of adsorption on the support as well. At this stage we are not concerned, except incidentally, with the co-adsorption of carbon monoxide and oxygen, since this is intimately connected with their reaction, and this is discussed later (Chapter 6). Figure 5.7 shows diagrammatically the various locations for carbon monoxide molecules on Au/TiC>2 for which there is some spectroscopic evidence. [Pg.141]

There are still a number of surface systems where the structure cannot be determined by LEED for theoretical and experimental reasons. High Miller-index surfaces, such as stepped or kinked surfaces, have layers separated by very small distances normal to the surface. The calculational tools normally used for LEED break down in this case, and no new approach has yet been developed to solve this problem. Experimental difficulties restrict the study of insulator surfaces, because of charging problems, and of molecular crystal surfaces, because of beam damage problems. [Pg.26]

Figure 3. The other common imperfection site on a (111) surface is a kink. This 7(111) X (310) surface shown in perspective is a regularly stepped and kinked surface with a step sequence beginning every seventh row and with a kink site at every third atom in the row. The atoms in kink sites have a coordination number of six... Figure 3. The other common imperfection site on a (111) surface is a kink. This 7(111) X (310) surface shown in perspective is a regularly stepped and kinked surface with a step sequence beginning every seventh row and with a kink site at every third atom in the row. The atoms in kink sites have a coordination number of six...
Acetonitrile and Methyl Isocyanide (8). Acetonitrile forms an ordered chemisorption state on the fully flat nickel surfaces, a p(2x2) and a c(2x2) on Ni(lll) and Ni(100), respectively. Acetonitrile thermal desorption from these two surfaces was nearly quantitative (a small amount of acetonitrile decomposed at the temperatures characteristic of the reversible thermal desorption from these surfaces). Importantly from an interpretive context, acetonitrile was quantitatively displaced from these two flat low Miller index planes by trimethylphosphine (8). However, the displacement was not quantitative (only 90-95% complete) from the stepped and stepped-kinked surfaces. For the super-stepped (110) surface, chemisorption was nearly irreversible and no acetonitrile could be displaced from this surface by trimethylphosphine. [Pg.286]

FIGURE 20.9 Schematic illustrating the PBC theory. In a simple cubic crystal, 100 faces are flat surfaces (denoted as F-faces) with one PBC running through one such surface, 110 are stepped surfaces (S-faces) that have two PBCs, and 111 are kinked surfaces (K-faces) that have three PBCs. (From Hartman, R, and Perdok, W.G., Acta CrystL, 8, 49, 1955.)... [Pg.343]

An extreme case of chemisorption-induced restructuring of metal surfaces is coirosive chemisorption as observed by SFG. In this circumstance, metal atoms break away from step or kink surface sites and form bonds with several adsorbate molecules. Carbon monoxide can form several carbonyl ligand bonds with platinum atoms leading to the creation of metal-carbonyl species. Thus, metal-metal bonds are broken in favor of forming metal-carbonyl clusters that are more stable at high CO pressures. The SFG vibrational spectra detect the reversible formation of new adsorb carbon monoxide species above 1(X) Torr on Pt(l 11), that appear to be platinum-carbonyl clusters Pt (CO) , with (m/n) > 1 and a CO commensurate overlayer. [Pg.56]

A notation for these surfaces, the compact-step notation, devised by Lang and Somoijai [3], gives the surface structure in the general form w h,k,l,) X (h kj,), where hjc,l,) and h kj,) are the Miller indices of the terrace plane and the step plane, respectively, while w is the number of atoms that are counted in the width of the terrace, including the step-edge atom and the in-step atom. Thus, the fcc(755) surface is denoted by 7(111) x 1(100), or also by 7(111) x (100) for simplicity. A stepped surface with steps that are themselves high-Miller-index faces is termed a kinked surface. For example, the fcc(10, 8, 7) = 7(111) X (310) surface is a kinked surface. The step notation is, of course, equally applicable to surfaces of bcc, hep, and other ciystals, in addition to surfaces of fee crystals. Stepped surfaces of several orientations are listed in Table 2.2 (p. 88). Here the crystal faces are denoted both by their Miller indices and by their stepped-surface notation. [Pg.47]

Figure 5. The flat stepped and kinked surfaces of platinum. (Photo credit Lawrence Berkeley Laboratories. Reproduced with permission from ref. 5. Copyright 1980 Elsevier Science Publishers.)... Figure 5. The flat stepped and kinked surfaces of platinum. (Photo credit Lawrence Berkeley Laboratories. Reproduced with permission from ref. 5. Copyright 1980 Elsevier Science Publishers.)...
Smdies of the rates of hydrogenolysis of the butanes on single-crystal surfaces are similarly scarce and unsatisfactory. On various platinum surfaces at 573 K dehydrogenation is the predominant process, followed by isomerisation, with hydrogenolysis only a very minor component. The last process was favoured by stepped or kinked surfaces (111) stmcture, whereas isomerisation preferred the (100) structure, but all clean single-crystal surfaces gave much higher activities... [Pg.553]

Results for stepped and kinked surfaces also given. [Pg.559]


See other pages where Kinked surface is mentioned: [Pg.1769]    [Pg.69]    [Pg.15]    [Pg.367]    [Pg.85]    [Pg.99]    [Pg.455]    [Pg.8]    [Pg.45]    [Pg.81]    [Pg.47]    [Pg.93]    [Pg.335]    [Pg.131]    [Pg.136]    [Pg.287]    [Pg.140]    [Pg.169]    [Pg.217]    [Pg.341]    [Pg.342]    [Pg.24]    [Pg.146]    [Pg.338]    [Pg.279]    [Pg.1769]    [Pg.84]    [Pg.421]    [Pg.220]    [Pg.95]    [Pg.236]    [Pg.629]   
See also in sourсe #XX -- [ Pg.47 ]




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