Ni原子活化氨分子理论研究

在UB3LYP/6-311＋＋G(3df,3pd)水平下, 详细研究了Ni活化NH₃分子的单重态和三重态势能面, 并用分子中的原子量子理论(Quantum Theory of Atom-in-Molecular, QTAIM)计算了势能面上所有驻点的性质. 计算结果表明, 单重态势能面有两条反应途径, 而三重态势能面仅有一条反应途径. 第一个N—H断开的活化能较低, 为99.96 kJ/mol, 活化自由能为100.86 kJ/mol,在常温下就可以进行; 第二个N—H键断裂所需能量高达200 kJ/mol, 不容易进行. 在合适温度下, Ni可以活化NH₃得到三重态HNiNH₂, 这表明Ni可以作为活化NH₃分子的良好催化剂.

Theoretical Study on the Activation of Ammonia by Ni atom

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.