Structural, electronic, and magnetic properties of MBn (M=Cr,Mn,Fe,Co,Ni, n≤7) clusters

We have investigated the stability, electronic, and magnetic properties of transition-metal-doped MBn clusters (M=Cr,Mn,Fe,Co,Ni, n≤7) using first-principles density functional theory with generalized gradient approximation. The equilibrium structures of MBn (n≤5) clusters can be obtained by directly adding M atoms to the Bn clusters, while for n=6, hexagon or near-hexagon geometries with a boron atom at the center ring are regarded as the ground-state structures. n=7 marks the onset of three-dimensional geometries for MBn clusters. According to the second-order energy differences, gaps between the highest occupied molecular orbital and lowest unoccupied molecular orbital and vertical ionization potentials, we can conclude that CrB4, CrB7, MnB3, FeB3, FeB5, FeB7, and CoB7 possess relatively higher stabilities. The relative orientation between the magnetic moments of the M atom and those of its neighboring B atoms mainly exhibits an antiferromagnetic alignment for CrBn, MnBn, and FeBn, while it mainly shows a ferromagnetic alignment for CoBn and NiBn clusters