Evolution of the electronic structure and properties of neutral and charged cobalt-doped aluminum clusters

Structural and electronic properties of neutral and ionic AlnCo (n = 8–17) clusters have been investigated by performing density-functional theory calculations within the effective core potential level. The total energies of these clusters are then used to study the evolution of their binding energy, relative stability, ionization potential, and vertical and adiabatic electron affinities as a function of size. Unlike the alkali atom-doped aluminum clusters in the same size range, the most cobalt atom resides inside the aluminum cluster cage except for Al12Co, Al13Co, Al11Co−, Al11Co+ and Al13Co+ clusters. Furthermore, the 3d and 4s energy levels of Co hybridize with the valence electrons of Al causing a redistribution of the molecular orbital energy levels of the Aln clusters. The binding energy evolves monotonically with size, but Al13Co, Al13Co− and Al13Co+ exhibit greater stability than their neighbors, which is consistent with the large HOMO–LUMO gaps. The calculated results agree reasonable with all available experimental data on ionization energies and electron affinities.