Density functional methods were used to study the structural and vibrational properties of NO adsorbed on the Ni atom and Ni-2 as well as the NO dimer ((NO)(2)) adsorbed on Ni-2. (NO)(2) is stabilized on Ni-2 with an optimized N-N bond distance of 1.61 Angstrom. A bonding analysis was performed to understand the mechanisms of adsorption and of the stabilization of the NO dimer on Ni-2. The significance of the stabilization of the NO dimer to the reaction path of NO adsorbed on metallic surfaces is also discussed briefly.