Using recent well-defined models of $\gamma \text{−}{\mathrm{Al}}_2{\mathrm{O}}_3$ surfaces in realistic pretreatment conditions, we study the interaction of ${\mathrm{Pd}}_n$ $(n=1-5)$ clusters and of a $\mathrm{Pd}\left(111\right)$ monolayer with the nonhydroxylated $\gamma \text{−}{\mathrm{Al}}_2{\mathrm{O}}_3\left(100\right)$ and the hydroxylated $\gamma \text{−}{\mathrm{Al}}_2{\mathrm{O}}_3\left(110\right)$ surfaces by means of density functional theory periodic calculations. We combine these results with previous results on the diffusion properties of a Pd single atom on these surfaces. The overall picture highlights the influence of metal coverage and hydration on the nucleation and growth of alumina supported Pd. The oxide support strongly decreases the exothermicity of the particle growth process. The results reveal that nucleation at very low metal coverage is more favorable on the hydrated surface than on the nonhydrated one, whereas, at a higher metal loading, the reverse becomes true. Finally, we calculate the work of adhesion of Pd films to investigate the wetting of large metallic particles. On the two investigated $\gamma \text{−}{\mathrm{Al}}_2{\mathrm{O}}_3$ surfaces, metallic particles are found to be in a bad wetting regime according to the Young-Dupré equation. For the hydroxylated (110) surface, the wetting is slightly weaker than for the nonhydroxylated (100) surface. The comparison with a hypothetic nonhydroxylated (110) surface reveals that surface hydroxylation even further reduces Pd particle wetting on the oxide.

• Received 18 July 2006

DOI:https://doi.org/10.1103/PhysRevB.75.045427