AN ABINITIO STUDY OF THE STRUCTURES, VIBRATIONAL-SPECTRA, AND ENERGETICS OF THE HOMOCYCLIC SULFUR MOLECULES S-4, S-5, S-6, S-7, S-8

High-level ab initio calculations have been employed to determine the geometries of cyclic Sn, n = 4-8. Gradient optimization was done at the SCF level with a polarized double-ζ basis set. Where available, agreement with experiment for the structures is better than has previously been available from ab initio calculations. Vibrational spectra were calculated for comparison to experiment. Energies relative to S8 have been obtained for n = 5-7. Comparison of energetic and spectroscopic calculations to experiment indicates that S4 is not a ring. The reaction S6 + S8 = 2S7 has a substantial entropy contribution to ΔG. © 1990 American Chemical Society.