Dependence of formation energies of tin nanoclusters on their size and shape

In a novel molecular beam experiment we have calorimetrically investigated the dependence of the Formation energies of isolated Sn-N clusters on their size. The experimentally determined size dependence of the formation energ y for Sn-N clusters consisting Of between 95 and 975 atoms can be explained by the existence of two different types of cluster isomers: One class of i somers is characterized by formation energies proportional to N-1/3, indica ting compact spherical-like shapes. The other class has constant formation energies for the investigated size range, which is consistent with quasi-on e-dimensional geometries.