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.