H+NH_3反应势能面的量子化学研究

Quantum chemical study of H+NH_3 reactive potential energy surface

本文采用UCCSD(T)/aug-cc-pVTZ方法研究了H+NH3反应势能面,获得了夺氢反应和交换反应过渡态的的几何结构和振动频率。夺氢反应的过渡态具有Cs对称性,其能垒为61.92 kJ/mol。交换反应的过渡态具有C3v对称性,其能垒为39.69 kJ/mol。H+NH3发生形成Td对称性的反应中间体NH4里德堡自由基。与夺氢反应相比,交换反应具有更低的反应能垒,并且NH4自由基在反应中可形成长寿命的共振态,和夺氢反应形成竞争关系,因此在H+NH3反应的量子动力学研究中必须同时考虑这两类反应。本文还采用更大的基组aug-cc-pVQZ和aug-cc-pV5Z研究了势能面对基组的收敛行为。

The potential energy surface of the reaction H ＋ NH3 has been studied with UCCSD （T）/aug-cc-pVTZ method. The geometry structures and vibrational frequencies of the transition states （TS） for both abstract and exchange reaction have been obta;ned. The ＇IS of abstract reaction has C, symmetry and the barrier height is 61.92 kJ/mol. The symmetry of the TS of exchange reaction is C3, and the barrier height is 39.69 kJ/mol. In exchange reaction there exists an intermediate NH4 redial which poses Td symmetry. The exchange reaction has some lower barrier height than that of abstract reaction and NH4 coldd form a long-life resonance state. This makes that the exchange reaction could challenge with the abstract reaction and is should be considered in the study of chemical dynamics. In the work the two another larger basis set are also used to study the convergence of energies.