The structures and stability of HNOS isomers

Potential energy surface of HNOS system is investigated by means of MP2 method with 6-311 ++ G(d, p) basis set. The energy for each minimum and saddle point on the potential energy surface is corrected at the QCISD(T)/6-311 ++ G(3df, 2p) level of theory with zero-point vibrational energy included. As a result, eighteen isomers are theoretically predicted and cis-HNSO is found to be global minimum on the potential energy surface. Wherein, fourteen isomers are considered as kinetically stable species, and should be experimentally observed. Comparisons are made for HNOS system with its analogues, HNO ₂ and HNS₂. The nature of bonding and isomers' stability of HNOS system are similar to HNS₂. The obvious similarities and discrepancies among HNOS, HNO₂ and HNS₂ are attributed to the hypervalent capacity of sulfur, oxygen and nitrogen atoms.