Binding energies of neutral silicon clusters

The binding energies per atom of neutral SiN-cluster size distributions with mean cluster sizes from N̄=65 to N̄=890 have been calorimetrically determined. The measured binding energies can be explained by the existence of two different classes of cluster isomers: One class is characterized by binding energies proportional to N−1/3, indicating compact spherical-like geometries. The other class has distinctly reduced binding energies, which do not show a dependence on the cluster size in the investigated size range. The binding energies of the calorimetrically investigated silicon clusters are discussed together with experiments on smaller silicon clusters with respect to the transition from bulk-like to molecular structures.