Molecular structures, energetics, and electronic properties of neutral and charged Hg_n Clusters (n = 2-8)

The geometric and electronic structures of small mercury clusters, Hg _n, Hg_n⁺, and Hg_n^- (n ≤ 8) have been calculated using a density functional theory. The results indicate that as the cluster size increases, the lowest energy states of neutral and anionic mercury clusters prefer three-dimensional structure whereas those of cationic clusters are peculiarly linear structure due to s-p hybridization. This structural feature has influence on the energetic and electronic properties of cationic clusters which deviate from the characteristics of van der Waals cluster. As the cluster size increases, energetic properties, binding energies per atom and second order difference in total energy of cationic clusters consistently decrease, in contrast to the neutral and anionic clusters. However, neutral and charged mercury clusters show common features in terms of size dependent transition of bonding character, such as the decrease of band gap and vertical ionization potential, and the increase of vertical electron affinity. These various properties are also qualitatively and quantitatively in line with the available experimental and theoretical results, implying the reliability of the ground state geometries of these clusters.