Coupled cluster study of the energetic properties of S2x (x=0,+1,1)

Ab initio electronic structure calculations are reported for S2, and its ions S2+ and S2-. Geometric parameters are calculated using the singles and doubles coupled cluster method, including a perturbational correction for connected triple excitation, together with systematic sequences of correlation consistent basis sets extrapolated to the complete basis set (CBS) limit. Energetic and structural properties of S2 and the S2 cation and anion are reported. The heat of formation of S2 (3Sigmag-) at 0 K in the gas phase is predicted to be 29.8 kcal/mol from the average of CBS two extrapolation procedures, less than the experimental heat of formation of S2 of 30.66+/-0.07 kcal/mol. The 0 K adiabatic ionization potential and electron affinity are predicted to be 9.37 and 1.68 eV, respectively.