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

摘要

The geometries, stabilities, and electronic and magnetic properties of Mg_nX (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 Mg_nFe, Mg_nCo, and MgnNi clusters have similar geometric structures and that the X atom in Mg_nX clusters prefers to be endohedrally doped. The average atomic binding energies, fragmentation energies, second-order differences in energy, and HOMO–LUMO gaps show that Mg_4X (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 Mg_(1,2,3,4,5,6,8,9)Fe, Mg_(1,2,4,5,6,8,9)Co, and Mg_(1,2,5,6,7,9)Ni, present high magnetic moments (4 μB, 3 μB, and 2 μB, respectively).