Cage doping of Ti, Zr, and Hf-based 13-atom nanoclusters: two sides of the same coin

Transition metal nanoclusters can exhibit unique and tunable properties which result not only from their chemical composition but also from their atomic packing and quantized electronic structures. Here, we introduce a promising family of bimetallic TM@Ti₁₂, TM@Zr₁₂, and TM@Hf₁₂ nanoclusters with icosahedral geometry, where TM represents an atom from groups 3 to 12. Density functional theory calculations show that their stability can be explained with familiar concepts of metal cluster electronic and atomic shell structures. The magnetic properties of these quasispherical clusters are entirely consistent with superatom electronic shells and Hund's rules, and can be tuned by the choice of the TM dopant. The computed cluster atomization energies were analyzed in terms of the elements' cohesive energy, E_coh, and contributions from geometric distortion, E_dis, surface energy, E_s, and ionic bonding, E_i. Some clusters have anomalous stability relative to E_coh + E_dis + E_s + E_i. We attribute this to superatomic character associated with a favorable atomic and electronic shell structure. This raises the possibility of designing stable superatoms and materials with tailored electronic and magnetic properties.