Density functional theory study of small X-doped Mgn ( X = Fe, Co, Ni, n=1-9) bimetallic clusters: equilibrium structures, stabilities, electronic and magnetic properties

The geometries, stabilities, and electronic and magnetic properties of MgnX (X = Fe, Co, Ni, n=1-9) clusters were investigated systematically within the framework of the gradient-corrected density functional theory. The results show that the MgnFe, MgnCo, and MgnNi clusters have similar geometric structures and that the X atom in MgnX clusters prefers to be endohedrally doped. The average atomic binding energies, fragmentation energies, second-order differences in energy, and HOMO-LUMO gaps show that Mg4X (X = Fe, Co, Ni) clusters possess relatively high stability. Natural population analysis was performed and the results showed that the 3s and 4s electrons always transfer to the 3d and 4p orbitals in the bonding atoms, and that electrons also transfer from the Mg atoms to the doped atoms (Fe, Co, Ni). In addition, the spin magnetic moments were analyzed and compared. Several clusters, such as Mg1,2,3,4,5,6,8,9Fe, Mg1,2,4,5,6,8,9Co, and Mg1,2,5,6,7,9Ni, present high magnetic moments (4 mu(B), 3 mu(B), and 2 mu(B), respectively).