Abstract: The structures, energetics, spectroscopies, and stabilities of the singlet NC₂S⁺ system were explored with density functional theory and ab initio method. At the B3LYP/6-311G(d) level, eight isomers were located, which are connected with 15 interconversion transition states. At the CCSD(T)/6-311+G(2df)//QCISD/6-311G(d)+ZPVE level, the lowest-lying isomer is linear NCCS⁺ 1(0.0 kJ/mol)with ¹Σ state followed by linear CNCS⁺ 2(54.8 kJ/mol). Two low-lying isomers 1, 2 and another high-lying species CCNS⁺ 3(323.8 kJ/mol) with a linear structure possess considerable kinetic stability. All the three isomers should be experimentally or astrophysically observable. The bonding natures of isomers 1, 2 and 3 were also analyzed.

Key words: Isomers, Potential energy surface, Structures, NC₂S⁺