Ab initio modeling of the metal-support interface:: The interaction of Ni, Pd, and Pt on MgO(100)

The interaction of Ni, Pd, and Pt on MgO has been investigated using cluster models and a variety of ab initio techniques. The case of a single Pd atom with acidic and basic sites of the MgO(100) surface has been chosen to test the adequacy of different ab initio wave functions and DFT techniques. Both approaches result in a similar description but only if large basis sets, including high angular momentum terms, and extensive treatment of the many-body effects are accounted for in the ab initio cluster model wave function. The DFT results appear to be more stable and less dependent on the basis sets. When properly compared, both approaches lead to the same conclusion. Pd interacts in a rather weak way with the acidic sites, but a moderately large interaction is predicted for interaction above the basic sites. Next, the interaction of Ni, Pd, and Pt on the basic sites of the MgO(100) surface is considered. The general trend is that the interaction energy increases from Ni to Pt. The nature of the bond is rationalized by analysis of the dipole moment curves and of the molecular orbitals.