Structures,stabilities and magnetic properties of small Co clusters

The lowest-energy geometric structures and their corresponding magnetic moments of Co_N $(N=2\text{–}13)$ clusters have been studied using first-principles method based on the density functional theory. In the calculation, the Jahn–Teller effect plays an important role because there are many isomers near the ground state for small cobalt clusters. And our results find that the magnetism is more sensitive to the symmetry relative to interatomic spacing and cobalt clusters grow in an icosahedral pattern. The results of the formation energy and the second derivative of binding energy show oscillatory behavior for small cobalt clusters and that 6-, 10- and 12-atom clusters are so-called magic clusters. Further, for the small cobalt clusters, the HOMO–LUMO gap and the mean magnetic moments show strong odd–even alternation as cluster size.