The possible formation of oxides or thin oxide films (surface oxides) on late transition-metal surfaces has recently been recognized as an essential ingredient when aiming to understand catalytic oxidation reactions under technologically relevant gas phase conditions. Using $\mathrm{CO}$ oxidation at $\mathrm{Pd}\left(100\right)$ as an example, we investigate the composition and structure of this model catalyst surface over a wide range of $(T,p)$ conditions within a multiscale modeling approach where density-functional theory is linked to thermodynamics. The results show that under the catalytically most relevant gas phase conditions a thin surface oxide is the most stable “phase” and that the system is actually very close to a transition between this oxidic state and a reduced state in terms of a $\mathrm{CO}$-covered $\mathrm{Pd}\left(100\right)$ surface.

• Received 30 January 2007

DOI:https://doi.org/10.1103/PhysRevB.75.205433

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