Local coordination numbers of up to 19 in gadolinium-tin alloy nanoclusters.

A combined approach based on quantum-chemical calculations and molecular beam experiments demonstrates that in isolated nanoalloy clusters of type GdSn, a total number of N = 19 tin atoms can be arranged around a central gadolinium atom. While the formation of the first coordination shell is incomplete for clusters with less than 15 tin atoms, the second coordination sphere starts to form for cluster sizes of more than 20 tin atoms. The magnetic properties of the clusters reveal that the tin atoms not only provide a hollow cage for Gd but also are chemically bound to the central atom. The calculated spin densities imply that an electron transfer from Gd to the tin cage takes place, which is similar to what is observed for endohedral metallofullerenes. However, the measured electric dipole moments indicate that in contrast to metallofullerenes, the Gd atom is located close to the center of the tin cage.