Isomers on the [S2, F2] potential energy surface: Straightening out experimental and theoretical findings using a high-level theoretical approach

CCSD(T) with a series of correlation consistent basis up to quintuple-zeta is used to investigate the structures, vibrational spectra, relative stability, heats of formation, and barrier to isomerization of S = SF2 and FSSF. It represents the most accurate characterization of these molecules to date. Including corrections for relativistic and core–valence correlation effects, we found −78.87 (−76.77) kcal/mol for ΔHf (298.15 K) of S = SF2 (FSSF). The accuracy of our results shows that the experimental NIST-JANAF value of −95.94 kcal/mol for S = SF2 is much overestimated, and sets a reference for a better estimate of the error bar in their value of −80.41 kcal/mol for FSSF.