Computational study on the doublet [H, S, Si, O] isomers: Structure, stability and dissociation

The structures, stability, thermochemistry and dissociation of the doublet [H, S, Si, O] species are studied using UMP2-FC and UCCSD(T)-FC methods. Twelve isomers connected with sixteen interconversion transition states are located on the doublet potential energy surface (PES). All isomers are planar except two cyclic isomers. The trans-HOSiS isomer is found to be the kinetically most stable species with the least interconversion barrier of 42.80 kcal/mol whereas the thermodynamically most stable cis-HOSiS isomer is the next kinetically stable species. Among the located isomers, five are found to be kinetically stable and should be observable experimentally. The dissociation processes of the [H, S, Si, O] species to the low-lying molecular fragments are investigated. The results are compared with those of analogous HOCO and HOCS species. Implications of these species in the laboratory and in interstellar medium are discussed. Finally the standard Enthalpies of formation at 0 K (ΔfH°, 0 K) is calculated for all [H, S, Si, O] species and their fragments.