Density Functional Study to Investigate the Ability of (ZnS)(n) (n = 1–12) Clusters Removing Hg(0), HgCl, and HgCl(2) 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 Hg(0), HgCl, and HgCl(2) 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 Hg(0) on (ZnS)(n) is physical adsorption and the adsorption ability of (ZnS)(n) for removing Hg(0) is weak. When (ZnS)(n) adsorbs HgCl and HgCl(2), 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)(n)HgCl and (ZnS)(n)HgCl(2). A partial density of states and charge analysis confirm that as Hg(0), HgCl, and HgCl(2) 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 HgCl(2) on (ZnS)(n) clusters are obviously bigger than those of Hg(0), indicating that HgCl and HgCl(2) adsorption on (ZnS)(n) clusters is much stronger than that of Hg(0). By combining ELF analysis, NCI analysis, and adsorption energies, the adsorption of HgCl, and HgCl(2) on (ZnS)(n) clusters can be classified as chemical adsorption. The adsorption ability of (ZnS)(n) clusters for removing HgCl and HgCl(2) is higher than that of Hg(0).