Structural, electronic, and magnetic properties of boron cluster anions doped with aluminum: B_nAl^- (2≤n≤9)

The geometrical structures, relative stabilities, electronic and magnetic properties of small B_nAl^- (2≤n ≤ 9) clusters are systematically investigated by using the first-principles density functional theory. The results show that the Al atom prefers to reside either on the outer-side or above the surface, but not in the centre of the clusters in all of the most stable B_nAl^- (2≤n ≤ 9) isomers and the one excess electron is strong enough to modify the geometries of some specific sizes of the neutral clusters. All the results of the analysis for the fragmentation energies, the second-order difference of energies, and the highest occupied-lowest unoccupied molecular orbital energy gaps show that B₄Al^- and B₈Al^- clusters each have a higher relative stability. Especially, the B₈Al^- cluster has the most enhanced chemical stability. Furthermore, both the local magnetic moments and the total magnetic moments display a pronounced odd-even oscillation with the number of boron atoms, and the magnetic effects arise mainly from the boron atoms except for theB₇Al^- and B₉Al^- clusters.