Stability of gold–polysulphide species: a DFT insight

Stability of gold–polysulphide species was investigated using density functional theory computations. Results showed that the stability of sulphur allotrope enhances with increasing number of sulphur atoms such that S8 is the most stable allotrope. For small allotropes (S2–S4), chain sulphur structures form the most stable geometries. However, for the larger allotropes (S5–S8), the cyclic structures are the most stable ones. The HOMO–LUMO gap showed a decreasing and an increasing trend for the chain and cyclic sulphur structures, respectively. Moreover, formation of S–Au is the most favourable sulphur–gold interaction among all the examined cases. Whereas, the formation of S5–Au and S6–Au compounds are also comparably favourable. S7 allotrope builds the weakest interaction with gold surface. The S8 as the most stable sulphur allotrope has a higher tendency towards gold surface, compared to the chain allotropes. The ultimate structure of sulphur allotropes formed as a result of polymerization were found to be isomers.