Systematic study on the structures and properties of (Ag2S)n (n = 1–8) clusters

Hollow polyhedral structures and properties of Ag2n-1Sn- (n = 2-11) clusters: A theoretical study

CONTEXT

The structures of Ag_2n-1S_n^- (n = 2-11) clusters are obtained by the combination of genetic algorithm (GA) and density functional theory (DFT). All the global minimum structures prefer hollow polyhedral structures, in which S-Ag-S element, triangular Ag₃S₃ and tetragonal Ag₄S₄ units present to stabilize the structures. The S atoms in the structures appear in μ₃-S or μ₄-S form. Adiabatic and vertical electron affinities of the clusters have been obtained, which reveals that they increases as cluster size. Stability analysis shows that Ag₉S₅^- and Ag₁₉S₁₀^- have special stability. The HOMO, LUMO orbitals of the clusters are obtained and the orbital components of them are calculated. The HOMO orbitals are mainly from the p orbitals of S atoms, whereas the s, p and d orbitals of Ag atoms contribute much bigger than the p orbitals of S atoms for LUMO orbitals. The orbital delocalization indexes (ODI) of the HOMOs and LUMOs are calculated, and the small ODIs of the HOMOs and LUMOs for n = 4-10 reveal that these orbitals are highly delocalized. By studying the projected density of states and molecular orbitals of Ag₉S₅^- and Ag₁₉S₁₀^- clusters, it is found that their molecular orbitals have superatomic properties. Superatomic properties play an important role in stabilizing clusters.

METHODS

This work used combined genetic algorithm and density functional theory (GA-DFT), and PBE0/Lanl2tz(Ag)/6-311G(d,p)(S) method to optimize the structures. Gaussian 16 program, Gauss view 6.0.16 program and Multiwfn 3.8 code are the softwares used.

Density Functional Study to Investigate the Ability of (ZnS)n (n = 1-12) Clusters Removing Hg0, HgCl, and HgCl2 via Electron Localization Function and Non-Covalent Interactions Analyses

In this study, the density functional theory is used to study the ability of (ZnS)_n clusters to remove Hg⁰, HgCl, and HgCl₂ and reveals that they can be absorbed on (ZnS)_n clusters. According to electron localization function (ELF) and non-covalent interactions (NCI) analyses, the adsorption of Hg⁰ on (ZnS)_n is physical adsorption and the adsorption ability of (ZnS)_n for removing Hg⁰ is weak. When (ZnS)_n adsorbs HgCl and HgCl₂, two new Hg-S and Zn-Cl bonds form in the resultant clusters. An ELF analysis identifies the formation of Hg-S and Zn-Cl bonds in (ZnS)_nHgCl and (ZnS)_nHgCl₂. A partial density of states and charge analysis confirm that as Hg⁰, HgCl, and HgCl₂ approach (ZnS)_n clusters, atomic orbitals in Hg and Zn, Hg and S, as well as Zn and Cl overlap and hybridize. Adsorption energies of HgCl and HgCl₂ on (ZnS)_n clusters are obviously bigger than those of Hg⁰, indicating that HgCl and HgCl₂ adsorption on (ZnS)_n clusters is much stronger than that of Hg⁰. By combining ELF analysis, NCI analysis, and adsorption energies, the adsorption of HgCl, and HgCl₂ on (ZnS)_n clusters can be classified as chemical adsorption. The adsorption ability of (ZnS)_n clusters for removing HgCl and HgCl₂ is higher than that of Hg⁰.