| 1 |
\contentsline {figure}{\numberline {1}{\ignorespaces The Pt(557) / 50\% CO system at a sequence of times after initial exposure to the CO: (a) 258\nobreakspace {}ps, (b) 19\nobreakspace {}ns, (c) 31.2\nobreakspace {}ns, and (d) 86.1\nobreakspace {}ns. Disruption of the (557) step-edges occurs quickly. The doubling of the layers appears only after two adjacent step-edges touch. The circled spot in (b) nucleated the growth of the double step observed in the later configurations.\relax }}{26} |
| 2 |
\contentsline {figure}{\numberline {2}{\ignorespaces Diffusion constants for mobile surface atoms along directions parallel ($\mathbf {D}_{\parallel }$) and perpendicular ($\mathbf {D}_{\perp }$) to the (557) step-edges as a function of CO surface coverage. Diffusion parallel to the step-edge is higher than that perpendicular to the edge because of the lower energy barrier associated with traversing along the edge as compared to completely breaking away. The two reported diffusion constants for the 50\% Pt system arise from different sample sets. The lower values correspond to the same 40\nobreakspace {}ns amount that all of the other systems were examined at, while the larger values correspond to a 20\nobreakspace {}ns period \relax }}{27} |
| 3 |
\contentsline {figure}{\numberline {3}{\ignorespaces Configurations used to investigate the mechanism of step-edge breakup on Pt(557). In each case, the central (starred) atom is pulled directly across the surface away from the step edge. The Pt atoms on the upper terrace are colored dark grey, while those on the lower terrace are in white. In each of these configurations, some number of the atoms (highlighted in blue) had a CO molecule bound in a vertical atop position. The energies of these configurations as a function of central atom displacement are displayed in Figure 4\hbox {}.\relax }}{28} |
| 4 |
\contentsline {figure}{\numberline {4}{\ignorespaces Energies for displacing a single edge atom perpendicular to the step edge as a function of atomic displacement. Each of the energy curves corresponds to one of the labeled configurations in Figure 3\hbox {}, and are referenced to the unperturbed step-edge. Certain arrangements of bound CO (notably configurations g and h) can lower the energetic barrier for creating an adatom relative to the bare surface (configuration a).\relax }}{29} |
| 5 |
\contentsline {figure}{\numberline {5}{\ignorespaces Points along a possible reaction coordinate for CO-mediated edge doubling. Here, a CO-bound adatom burrows into an established step edge and displaces an edge atom onto the upper terrace along a curvilinear path. The approximate barrier for the process is 20\nobreakspace {}kcal/mol, and the complete process is exothermic by 15\nobreakspace {}kcal/mol in the presence of CO, but is endothermic by 3\nobreakspace {}kcal/mol without.\relax }}{30} |
| 6 |
\contentsline {figure}{\numberline {6}{\ignorespaces Dynamics of an established (111) double step after removal of the adsorbed CO: (A) 0\nobreakspace {}ps, (B) 100\nobreakspace {}ps, and (C) 1\nobreakspace {}ns after the removal of CO. The presence of the CO helped maintain the stability of the double step. Nearly immediately after the CO is removed, the step edge reforms in a (100) configuration, which is also the step type seen on clean (557) surfaces. The step separation involves significant mixing of the lower and upper atoms at the edge.\relax }}{31} |
