Equilibrium geometries and electronic properties of binary transition-metal clusters, (NbCo)(n) (n Nb-Co>Co-Co. As the binary cluster size increases, the Nb-Co bond may become stronger than the Nb-Nb bond in the inner niobium core, which results in a remarkable increment of the Nb-Nb bond length. Amongst these binary transition-metal clusters, the singlet (NbCo)(4) in T-d symmetry has a striking high stability due to the presence of the spherical aromaticity and electronic shell closure. The size dependence of the bond length and stability of the cluster has been explored. (C) 2005 American Institute of Physics
