Abstract: The geometric structures of the eight kinds of configurations of S₄ have been optimized by using SCF-HF ab initio, MP2 and two density functional methods (BLYP, B3LYP) with 6-311+G^** basis set. Vibrational spectra have been computed for each configuration respectively by HF and B3LYP methods. Total energies have been calculated with the MP4/6-311+G** and the QCISD(T)/6-311+G^** levels for electron correlation effects us ing HF/6-311+G^** geometries. The relative stabilities of the different co nfigurations are compared to each other. It is concluded that S4 has a cis-planar C_2v ground state strcture.

Key words: S4 molecule, vibrational spectra, ab initio, density functional methods