ON THE INFLUENCE OF TOPOLOGY ON THE ENERGY PROFILE IN METALLIC PD CLUSTERS

A main ingredient to model the physics of metallic clusters is the kno wledge of the spatial and energetic distribution of the atoms. Quenche d molecular dynamics simulations with interatomic potentials derived f rom the electronic structure (tight-binding approximation) show that P d cubo-octahedral and icosahedral clusters undergo an inhomogeneous co ntraction, restricted to the surface selvedge and, in the latter case, to the inner core. This wrinkled profile leads to interatomic distanc es which can be larger than the bulk Pd ones for icosahedral clusters, whereas they all are smaller for cubo-octahedral clusters. Moreover i t induces, for the icosahedral shape, the occurrence of a core energy in the energy profile, which leads to a structural transition from ico sahedron to cubo-octahedron when the cluster size reaches about 2000 a toms.