AN ABINITIO STUDY OF THE POLYSULFANE SERIES H2S2 TO H2S6 AND OF S8

6-31G** and pseudopotential SCF calculations were performed for the polysulfane series H2S(n), n = 2-6 and for S8. Energy-optimized structures and harmonic vibrational frequencies were calculated and compared with experimentally determined values where possible. The torsional barriers to the rotation of the HS bond in H2S2 and H2S3 are discussed. From the results obtained for the polysulfane series we also obtained geometries and force constants for the infinitely extended sulfur chain. These data were used to compute the phonon dispersion curves of helical S-infinity. In agreement with previous experimental and semiempirical investigations it was found that the strain in the S8 ring is small compared with that in strain-free chains.