Efficient Eley-Rideal Reactions of H Atoms with Single Cl Adsorbates on Au(111)

Density functional theory is used to construct an interaction model for H atoms with Cl over Au(111). Single-adsorbate Eley-Rideal reactions are investigated with quantum and quasiclassical methods. The reaction cross sections, amounting to $2–3{\AA }^2$, are much larger than for HD recombinations on metals. This can be traced to the adsorbed Cl being relatively far above the surface, the H-Cl interaction prevailing over the H-substrate attraction for a sizable range of impact parameters.

Figure 1

Potential energy curves for both Cl and H atoms located over the hollow site of Au(111), in a collinear configuration. The potential energy is plotted as a function of the distance of the incident H above the surface plane, for the four Cl positions indicated. The symbols correspond to the DFT calculations, and the lines to the model PES.

Figure 2

Quasiclassical (QC) reaction probability as a function of the impact parameter $b$, for H at normal incidence with initial energy $E_i$, as indicated. The Cl atom is initially in the ground vibrational state ${\nu }_i=0$. Both the QC and the quantum reaction cross sections $\sigma$ are listed in the inset.

Figure 3

Same as Fig. 2, except that ${\nu }_i={\nu }_{\mathrm{C}\mathrm{l}}=0–5$, as indicated, and $E_i=0.07\mathrm{e}\mathrm{V}$.