The activation of ammonia by Ni atom was investigated at the UB3LYP/6-311＋＋G(3df,3pd) level. All the stationary points were analyzed by the Quantum Theory of Atom-In-Molecule (QTAIM). The computational results indicate that the singlet state contains two reaction channels, while the triplet includes only one reaction channel. The free energy barrier for the activation of the first N—H bond is 100.86 kJ/mol at 298.15 K and 101.325 kPa, thus it is feasible at room temperature. However, the activation of the second N—H to form the H₂NiNH intermediate is very difficult, because its energy barrier is higher than 200 kJ/mol. Therefore, Ni is a good catalyst for the activation of NH₃ to form NH₂ radical.

Key words: N—H bond activation, Ni catalyst, density functional theory, quantum theory of atom-in-molecule