Modeling free and supported metallic nanoclusters: structure and dynamics

Abstract

We compare atomic structure and dynamics of free and supported metallic clusters via molecular dynamics simulations using tight-binding semiempirical potentials for metal–metal interactions and a potential fitted to ab initio calculations for the metal-supported ones, the support being essentially the MgO(100) surface in the case of a nonreactive metal–oxide interface. The structural transition for free Ni, Pd, Pt, Cu, Ag, Au clusters with noncrystalline structures (mainly icosahedral and decahedral) at small sizes to FCC truncated octahedrons for larger sizes is reported as well as the variation of the critical size of transition from 3d to 5d metals. In the case of Pd clusters on the MgO(100) surface, we analyze the substrate-induced modifications in morphology and atomic structure and follow their evolution as a function of cluster size. The mechanism of strain release by misfit interfacial dislocations in 3D clusters is described at the atomic level. Dynamics of growth and melting of free silver clusters are discussed and some effects of the oxide substrate in melting transition are pointed out, notably the delay in melting induced by the epitaxial relation with the support.

Keywords:

• Metallic nanoclusters
• Solid–liquid phase transition
• Structural transitions
• Molecular dynamics simulations

Acknowledgements

F. Baletto and R. Ferrando acknowledge support from the Italian MURST under the project “Nuove frontiere della fisica delle superfici, dei nanofili e dei nanoclusters”’. The CRMC2 is associated to the Universities of Aix-Marseille II and III.