Plane indices

Empirically, however, the results are reasonably accurate, and the approach is a very useful one. An application of it to various Miller index planes is given by... 

Most fiindamental surface science investigations employ single-crystal samples cut along a low-index plane. The single-crystal surface is prepared to be nearly atomically flat. The surface may also be modified in vacuum. For example, it may be exposed to a gas that adsorbs (sticks) to the surface, or a film can be grown onto a sample by evaporation of material. In addition to single-crystal surfaces, many researchers have investigated vicinal, i.e. stepped, surfaces as well as the surfaces of polycrystalline and disordered materials. 

Beebe T P, Goodman D W, Kay B D and Yates J T Jr 1987 Kinetics of the activated dissociation adsorption of methane on low index planes of nickel single crystal surfaces J. Chem. Phys. 87 2305... 

An alternative, but to some extent complementaty approach to the structure of grain boundaries notes that as the tilt angle between the crystals forming the grain boundary increases, planes of lower atomic concentrations, the high index planes, such as (221), (331) and (115) in the face-centred strucmre, become parallel to the grain boundary. There is therefore a decrease in the number of metal-metal bonds at the boundary as the tilt angle increases. 

Such simple considerations led Scholten and Konvalinka to confirm the form of the dependence of the reaction velocity on the pressure, as had been observed in their experiments. Taking into account a more realistic situation, on the polycrystalline hydride surface with which a hydrogen molecule is dealing when colliding and subsequently being dissociatively adsorbed, we should assume rather a different probability of an encounter with a hydride center of a /3-phase lattice, an empty octahedral hole, or a free palladium atom—for every kind of crystallite orientation on the surface, even when it is represented, for the sake of simplicity, by only the three low index planes. 

D and fractional exponent a (Table 15) show that the surface of electrochemically polished Cd electrodes is flat and free from components of pseudo-capacitance. The somewhat higher values of D for electrochemically polished high-index planes and for chemically treated electrodes indicate that the surface of these electrodes is to some extent geometrically and energetically inhomogeneous. However, the surface of chemically treated Cd electrodes, in comparison with the surface of mechanically polished or mechanically cut electrodes, is relatively... 

Gregory BW, Suggs DW, Stickney JL (1991) Conditions for the deposition of CdTe by electrochemical atomic layer epitaxy. J Electrochem Soc 138 1279-1284 Suggs DW, Stickney JL (1991) Characterization of atomic layers of tellurium electrodeposited on the low-index planes of gold. J Phys Chem 95 10056-64 Suggs DW, Stickney JL (1993) Studies of the structures formed by the alternated electrodeposition of atomic layers of Cd and Te on the low-index planes of Au. 1. LEED and Auger studies. Surf Sci 290 362-374... 

Suggs DW, Stickney JL (1993) Studies of the surface structures formed by the alternated electrodeposition of Cd and Te on the low-index planes of Au. II. STM studies. Surf Sci... 

Hayden BE, Nandhakumar I (1997) In-situ STM Study of Te UPD layers on low index planes of gold. J Phys Chem B 101 7751-7757... 

Structure Sensitivity over Pe. Table II presents the rates of ammonia synthesis over each of the low Miller index planes of Pe. 

Since oxidation of methanol is an electrocatalytic reaction with different adsorption steps, interactions of the adsorbed species with the metallic surface are important. Using platinum single-crystal electrodes, it has been proven that the electrooxidation of methanol is a surface-sensitive reaction. The initial activity of the Pt(llO) plane is much higher than that of the other low-index planes, but the poisoning phenomenon is so rapid that it causes a fast decrease in the current densities. The... 

For both reactions studied, NO+CO and NO+propene, the effect of electrochemically pumped Na in increasing the extent of NO dissociation is large and significant. This is because unpromoted low index planes of Pt, Pt(lll), are relatively inert towards NO dissociation and we adscribe the NO dissociation as the key reaction-initiating step. Such dissociation of diatomic molecules in the field of coadsorbed cations has been discussed in detail by Lang et al [29], The rates of production of CO2. N2 and NjO all depend on... 

The qualitative voltammetric behavior of methanol oxidation on Pt is very similar to that of formic acid. The voltammetry for the oxidation of methanol on Pt single crystals shows a clear hysteresis between the positive- and negative-going scans due to the accumulation of the poisoning intermediate at low potentials and its oxidation above 0.7 V (vs. RHE) [Lamy et al., 1982]. Additionally, the reaction is also very sensitive to the surface stmcture. The order in the activity of the different low index planes of Pt follows the same order than that observed for formic acid. Thus, the Pt(l 11) electrode has the lowest catalytic activity and the smallest hysteresis, indicating that both paths of the reaction are slow, whereas the Pt( 100) electrode displays a much higher catalytic activity and a fast poisoning reaction. As before, the activity of the Pt(l 10) electrode depends on the pretreatment of the surface (Fig. 6.17). 

There exist two geometrically different varieties of these sites, which are referred to as B5 sites because both can be made to accommodate a nitrogen molecule, which is then coordinated by five atoms. They occur at steps on the (100) and (111) planes, and particularly on (110), (311), and other high-index planes. A later paper by van Hardeveld and van Montfoort (10) contains additional evidence showing that the B5 sites are indeed responsible for the infrared-active form of nitrogen adsorption, and also that the number of B5 sites in the sample can be estimated with fair accuracy from the intensity of the 2200 cm-1 band. This means that infrared study of nitrogen adsorption can give valuable information about the structure of the surface of metal particles. 

There are great similarities between the atomic layer structures formed by Te, Se and S on the low index planes of Au [238]. Table 2 shows a listing of structures... 

Some atomic level studies of CdSe formation have been performed, using STM, AES and LEED [161, 162]. The structures formed by reduction of HScO, on the low index planes of Au are described in a number of papers [237, 238, 240, 241], in Section 7.2.3, and are listed in Table 2, for the low index planes of Au. 

Stranski-Krastanov growth has been documented for copper on Au(lll) [101, 102], Pt(100) and Pt(lll) [103], for silver on Au(lll) [104, 105], for cadmium on Cu(lll) [106] and for lead on Ag(100) and Ag(lll) [107-109]. In all of these examples, an active metal is deposited onto a low-index plane of a more noble metal. Since the substrate does not undergo electrochemical transformations at the deposition potential, a reproducible surface can be presented to the solution. At the same time, the substrate metal must be carefully prepared and characterized so that the nucleation and growth mechanisms can be clearly identified, and information can be obtained by variation of the density of surface features, including steps, defects and dislocations. 

A.R. Siedle, 3M Central Research Laboratory If one of the extended structures described by Professor McCarley were truncated through a low Miller index plane, can one, following the appproach of Solomon, predict what metal orbitals would protrude from the surface so generated Have ultraviolet photoelectron spectra been obtained on single crystals of any of these materials ... 

Cu(111) to a lesser extent than on the other two low-index planes. This adsorption results in formation of an ordered structure above 103 L at room temperature, which is displayed as an oblique unit cell [ ]. This pattern has been previously reported (16). It is interesting that it has not been observed by other workers, possibly because of the extreme O2 exposures required and the faintness of the pattern. 

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