Structures and Stabilities of Pbn (n ≤ 20) Clusters

We have performed global structural optimizations for neutral lead clusters Pb(n) (n = 2-20) by using a genetic algorithm (GA) coupled with a tight-binding (TB) potential. The low-energy structures identified from a GA/TB search were further optimized at the DFT-PBE level. The calculated results show that the Pb(n) (14 < n </= 20) clusters favor compact spherical structures with hexagon and pentagon rings. These structures are different from those of Si(n), Ge(n), and Sn(n) clusters which favor prolates in the same size range. The binding energies, second differences in energy, and fragmentation behaviors of the Pb(n) clusters were also discussed. Pb(n) (n = 4, 7, 10, 13, 15, and 17) clusters are found to be special stable clusters, which is in good agreement with the experimental results.