The reaction of Ni+ with CS2 has been investigated at B3LYP/TZVP and B3LYP/6-311 + G* levels of theory. The reaction mechanisms have been explored in detail on both doublet and quartet potential energy surfaces. The products observed in the experiment have been explained according to the cleavage of different bonds in the insertion intermediate S-Ni+-C-S. The product [Ni, C, S](+) observed in experiment was confirmed as Ni-CS+ ((2)Sigma). The spin-forbidden reaction Ni+(D-2) + CS2 -> NiS+((4)Sigma) + CS ((1)Sigma) was found to proceed through a doublet-quartet surface crossing and the crossing seam was approximately calculated. (C) 2008 Elsevier B.V. All rights reserved.