Hcp metal nanoclusters with hexagonal A-A bilayer stacking stabilized by enhanced covalent bonding

Abstract

First-principles total energy calculations within density functional theory have been performed to study the geometric and electronic structures of Run nanoclusters of varying size n (14≤n≤42). Strikingly, for the size range of n=14 to 38, the clusters always prefer a hexagonal bilayer structure with A-A stacking, rather than some of the more closely packed forms, or bilayer with A-B stacking. Such an intriguing "molecular double-wheel" form is stabilized by substantially enhanced interlayer covalent bonding associated with strong s-d hybridization. Similar A-A stacking is also observed in the ground states or low-lying isomers of the clusters composed of other hcp elements, such as Os, Tc, Re, and Co. Note that these "molecular double-wheels" show enhanced chemical activity toward H2O splitting relative to their bulk counterpart, implying its potential applications as nanocatalysts. © 2010 The American Physical Society.