Probing Pd_n (n=1-5) Clusters on Rutile TiO₂ Surfaces by Using First-Principle Calculations

Small metal clusters with novel structures, which have interesting perporties and important potential applications, could be stabilized by substrate surfaces. In this work, by using density functional theory (DFT) calculations, we studied the geometric and electronic structures of Pd_n (n=1-5) clusters supported on the well-studied (110) surface and (100) and (001) surfaces of rutile TiO₂ together. It is found that the surface plays a vital role in stabilizing Pd cluster structure. The (110) surface influences slightly on the geometries of Pd clusters, where Pd cluster on the TiO₂(100) surface prefers to grow as a linear mode. The Pd_n cluster are obviously diffused by the (001) surface because of the strong interaction between Pd and TiO₂ substrate where the adsorption energy ranges from −3.54 to −6.57 eV. Pd₁/TiO₂(001) is predicted to be stable because the nucleation from Pd₁ to Pd₂ on TiO₂(001) is an endothermic process. All the Pd_n clusters are positively charged while the 4d orbitals of Pd are predominant near the Fermi level.