Theoretical studies on structure, isomerization, and stability of [Si, O, S]

The structures, energetics, and isomerization of a possible interstellar [Si, O, S] system were explored at the CCSD(T)/aug-cc-pVQZ//CCSD(T)/aug-cc-pVTZ level. On the schemaitc potential energy surface(PES), we found that silicon oxysulfide(OSiS) produced in laboratory is the global minimum. An analysis of the Wiberg bond index(WBI), bond order and the bond length, shows that silicon oxysulfide contains SiO and SiS double bonds in accordance with the results of Schnöckel. Besides silicon oxysulfide, another interesting cyclic minimum(c-SiOS) was found to have a very high kinetic stability stabilized by the least barrier of 120.9 kJ/mol. In light of the fact that no cyclic sulfide-containing species has been detected in space, c-SiOS could be a very promising candidate. The presented results might provide useful information on detected interstellar molecules O=Si=S and c-SiOS.