Computational study on structures, isomerization, and dissociation of [Si, N, C, S]⁺ isomers

A singlet potential energy surface (PES) of the [Si, N, C, S]⁺ system is investigated by means of MP2 and QCISD(T) (single-point) methods. Four linear isomers of [Si, N, C, S]⁺ system are found to be kinetically stable and should be experimentally observable. The linear isomer SiNCS⁺ is the thermodynamically most stable, followed by SSiCN⁺, SSiNC⁺ and SiCNS⁺. No cyclic kinetically stable isomers are found. For the isomer SiNCS⁺, several isomerizations can very favorably compete with its direct dissociation, and thus, the very recent mass spectrometric experiment can reasonably be interpreted by analyzing the structures and bonding.