How “Magic” is a Magic Metal Cluster?

The stability of a closed-shell metal cluster, ${\mathrm{Na}}_8$, is studied in a variety of surroundings using ab initio molecular dynamics. On the insulating NaCl(001) surface, ${\mathrm{Na}}_8$ is magic; even at 600 K it retains its intrinsic structure. On the Na(110) surface it spontaneously collapses, forming an epitaxial adlayer. In the vacuum, interaction with another ${\mathrm{Na}}_8$ cluster destroys its shell structure and a deformed ${\mathrm{Na}}_{16}$ is formed. The results are discussed in a context relevant to cluster-assembled structures.