On the thermal stability of the branched hexasulfane isomers. A DFT molecular dynamics study of H2S6 conformers

Using Born–Oppenheimer DFT molecular dynamics we address the stability and non-harmonic vibrational effects of the three isomers of hexasulfane at 300 K and 700 K. Both branched structures are stable and dynamic effects introduce large changes to the SS distances due to the oscillating behavior between SSSS and SSSS structures. The largest non-harmonic effects (40%) are found for isomer B in the low frequency region corresponding to the torsional mode coupling the two HS3–S3H moieties. The simultaneous detection of the peaks shifts in the 250 and 800 cm−1 regions could be used to unequivocally characterize these branched hexasulfane isomers in sulfur melts.