Signature of crystalline order in ultra-small metal-oxide clusters

First principles calculations of the equilibrium geometries, binding energies, electronic structure and ionization potentials of SbxOy clusters reveal that clusters as small as Sb5O7 bear the fingerprint of their crystal structure. Electronic structure of even smaller clusters mimics the bulk behavior. A partial ionic bonding between metal and oxygen atoms leads to a new family of magic numbers for (x, y)=(2, 3), (3, 4), (4, 5) and (5, 7). Simple rules are provided for constructing geometries of larger magic clusters.