Surface atomic configuration, Schematic

Figure 11.1 Schematic illustrations of the atomic configuration of (a) (100), (111), and (b) (110) surfaces of fee symmetry, together with the corresponding unit cell of each surface. The surface energy per atom of a specific surface can be estimated by counting the total number of...

One important aspect not discussed above is the change in atomic structure at a surface. Contrary to the schematic picture of the Si(lll) surface shown in Fig. 14.6, a solid surface is usually not just the end of a perfect crystal. Surfaces reconstruct in response to the changes in the electronic distribution caused by the surface itself. Again, all these changes occur selfconsistently, and in principle, if the total energy for various configurations of atomic structures at a surface could be evaluated, the shifts in the positions of the atoms and the electronic structures of the surface could be determined theoretically. This approach will be discussed in the next section, but the first calculations for reconstructed surfaces were done using experimental determinations of the atomic positions. 

Fig. 3. LEED patterns and schematic representations of the surface configurations of platinum single-crystal surfaces, (a) Pt(Ill) containing less than 1012 defects/cm2, (b) Pt(557) face containing 2.5 x 1014 step atoms/cm2 with an average spacing between steps of 6 atoms, and (c) Pt(679) containing 2.3 x 10 4 step atoms/cm2 and 7 x 1014 kink atoms/cm2 with an average spacing between steps of 7 atoms and between kinks of 3 atoms.

Fig. 10 Schematic representation of the Ni(llO) surface with four Au atoms in the overlayer. Open circles indicate Ni atoms in the surface layer, Au atoms in the overlayer are indicated by black disks. These configurations correspond to a Au coverage of 0.067 ML.

The formation of cp chains, both in the overlayer or surface, is a characteristic shared by both systems which also appears in any favored ternary configuration. In Fig. 36 we schematically represent the influence of each one of the individual processes in the observed behavior of the ternary system, including new features that arise from the interaction of Cu and Au atoms. 

Figure 3.12 Schematic representation of DNA wrapping around a CNT (inset) and an initial configuration of the C-oligomer wrapped along the (6,5) tube chirality. Carbon atoms of the CNT marked by light gray indicate the direction of DNA wrapping with seven cytosine bases per helical turn, which lay parallel to the tube surface and nearly normal to the tube chiral vector, thus increasing the n-jt overlap between the base and tube orbitals. Reprinted with permission from ref. 120. Copyright 2009 American Chemical Society.

FIGURE 7.11 Implementation of a defect exposing Cu atoms on the O-enriched passive film for copper in interaction with a 20M CF aqueous solution (pH 7). Left schematic top view of the unit cell at the passive film surface. The circular defect (radius of 0.8 nm) is configured using periodic boundary conditions. Middle side view of the unit cell for the complete system. Right side view after 300 ps relaxation showing Cl adsorption and pit nucleation at the implemented defect and defects generated in the bulk substrate around the defects site. Adapted from Jeon et al. [135], 1229, with permission from the American Chemical Society. 

Fig. 9 Left A schematic illustration of the Pt(n0)- 1 x 2) surface showing the directions of the atomic relaxations derived from fits to the X-ray scattering data. In the top view, the letter X indicates the most likely site for hydrogen adsorption. Right (a) The CV of a Pt(llO) disk electrode measured in an RRDE configuration (20 mV s ). The symbols correspond to the charge associated with hydrogen and hydroxyl adsorption, (b) TheXRV measured at (0,0,1.55) forthe positive (symbols) and negative (dashed line) sweep directions (2 mV s ).

Fig. 38. Schematic representation of surfaces exhibiting one-atom step height configuration, multiple-height step structure, and hill-and-valley configuration consisting of large facet planes. Reconstruction from one type to another may occur on adsorption and/or heating...

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