Structure of Ag-Pd nanoclusters adsorbed on MgO(100): A computational study

The structures of AgPd clusters supported onMgO(100) are investigated via a combination of global optimization searches within an atom–atom potential model and density-functional calculations. Although pure Ag and Pd clusters favor fcc structures in (100) epitaxy with the substrate, it is found that AgPd mixing creates a pocket of stability for polyicosahedral structures in the AgPd/MgO(001) nanoalloy phase diagram. Polyicosahedra are very stable for size around 40 atoms, where they compete with fcc(100) and decahedral structures. For clusters with up to 200 atoms and 50%–50% composition, these last two structuralmotifs are themost stable ones at the atom– atom potential level. For sizes of 400 atoms, fcc structures in (111) epitaxy with the substrate become close in energy to fcc(100) and Dh clusters, indicating a likely transition to (111) epitaxy for larger sizes.