Palladium nano-clusters on the MgO(1 0 0) surface: substrate-induced characteristics of morphology and atomic structure

Abstract

As a model catalyst, late transition and noble metal nano-clusters supported on MgO(1 0 0) have been the subject of numerous detailed experimental studies. Understanding their morphology, the relation between their size, the detailed atomic structure, and the interaction with the oxide substrate is a first and necessary step towards the control of their reactivity. From the theoretical point of view, if ab initio methods have proved their usefulness in the description of interactions at metal/oxide interfaces, the computational effort necessary for a realistic description of larger-size systems disables their use for simulations of cluster structures which have been experimentally observed. This is why we have proposed an effective approach to simulate non-reactive deposition of nano-scale metal objects on surfaces of highly ionic oxides. Its core is a many-body potential energy surface derived from results of ab initio calculations for model metal/oxide interface structures. In the present paper, we focus on palladium clusters deposited on the MgO(1 0 0) surface, with special interest in the smallest particle sizes. Using molecular dynamics simulations we analyse the transformation of the free clusters in contact with the substrate and the substrate-induced characteristics of their supported equilibrium morphology. We also report on the existence of well-defined magic numbers, different from those characteristic for free particles, and relate them to the particular features of interaction at the metal/oxide interface.