The reactions between Ni (d(10) S-1) and CH4 have been carried out at the B3LYP/6-311+G(2d, 2p) and B3LYP/6-311++G(3df,2p) theoretical levels. The reaction path in which the intermediates transfer from one to another via transition state is rationalized by their structures and natural bond orbital analysis. The reactions of Ni + CH4 --> NiCH2 + H-2, Ni + CH4 --> NiCH3 + H and Ni + CH4 --> NiH + CH3 are predicted to be endothermic, and the reaction Ni + CH4 --> NiH + CH3 is the easiest to occur. (C) 2002 Elsevier Science B.V. All rights reserved.