Characteristics of Pd adsorption on the MgO(100) surface: Role of oxygen vacancies

Using the ab initio full-potential linearized augmented-plane-wave approach, we have studied the role of surface oxygen vacancies on the characteristics of palladium deposition on the MgO (100) surface, In agreement with recent theoretical evidence, we find that the adsorption energy of a single Pd atom is considerably enhanced by the defects, and that an important electron transfer from the substrate towards the adsorbed Pd atom occurs. By considering three types of palladium deposits-a single atom, a monolayer, and a bilayer-we have analyzed the evolution of the vacancy-induced interface properties as a function of the dimensionality of the deposit and we show that the modifications reported for the isolated Pd adatoms are to a large extent present also for more extended deposits. However, the electron transfer across the interface remains localized to the close vicinity of the oxygen vacancy, and the stabilization effect of vacancies is particularly strong on lower-coordinated metal atoms. This indicates that the major vacancy-induced modification of the deposit shall be Limited to those metal atoms at the cluster edges that adsorb directly at the vacancies.