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

Silver sulfide is a famous semiconductor, which can be used in many areas. Understanding the size evolution of silver sulfide clusters is useful in controlling their size to improve their properties in applications. The structures of (Ag₂S)_n (n = 1-8) clusters are explored using a combined method of genetic algorithm (GA) and density functional theory (DFT). The TPSSh/def2-tzvp(Ag)/6-311G(d)(S) method has been used to optimize the structures. The re-optimized structures and refined energies are computed at PBE0/Lanl2tz(Ag)/6-311G(d,p)(S) level according to the benchmark calculations. The global minimum (GM) structures, HOMO and LUMO frontier orbitals, density of states, ionization potentials, electron affinity energies, noncovalent interactions, and natural populations of the clusters have been studied. The clusters evolve from open to cage structures when n varies from 1 to 8. A triangular Ag₃S₃ unit is found to be an important building block, which can construct the global minimum structures of (Ag₂S)_n (n = 3-8) clusters. When n > 6, quadrangular Ag₄S₄ rings present in (Ag₂S)_n clusters. (Ag₂S)₆ and (Ag₂S)₈ clusters are in hollow conformation, and both of which have special stability because of their high HOMO-LUMO gaps, high ionization potentials, and Ag⋯Ag attractive interactions in them. Graphical abstract.