It was noted that the nucleation of metal clusters on oxide surfaces was typically dominated by defect sites. Rate equation models of defect nucleation were developed and applied to these systems. By comparing the models with nucleation density experiments, energies for defect-trapping, adsorption, surface diffusion and pair binding were deduced; notably for Pd deposited onto Ar-cleaved MgO(001). However, the defects responsible remained largely unknown. Several types of ab initio calculations had been made of these energies for Pd and related metals on MgO(001) containing several types of surface defect. The calculated values were reviewed here, and some were found to be widely divergent. New rate-equation nucleation density predictions were performed using the calculated values. The calculations, for some defect types, were much closer to experiment than were others. The singly charged Fs+ center and the neutral divacancy were identified as being candidate defects. In these 2 cases, the Pd/MgO(001) nucleation density predictions agreed well with experiment. Energy and entropy values were considered with regard to differences in calculated charge redistributions between the metal atoms, clusters and (charged) surface defects, and cluster geometries.

Nucleation and Growth on Defect Sites - Experiment–Theory Comparison for Pd/MgO(001). J.A.Venables, L.Giordano, J.H.Harding: Journal of Physics - Condensed Matter, 2006, 18, S411-27