First-principles calculations for structures and absorption optical spectra of sulfur cluster S7

A finite-difference pseudopotential density-functional theory in real space and Langevin molecular dynamics annealing technique are applied to determine the ground state structure of sulfur cluster S7 and the corresponding optical absorption spectra from a linear response method within the adiabatic time-dependent local density approximation. It is found that the ground state structure of sulfur cluster S7 belongs to a chair structure with Cs symmetry and the calculated spectra exhibit a variety of features that can be used for comparison against future experimental investigations