NH3与CaH2反应机理的密度泛函理论研究
Theoretical study on the reaction between NH3 and CaH2

基于密度泛函理论（DFT）当中的B3LYP（杂化密度泛函）方法，于6-311G(d, p)基组水平上对NH3与CaH2的反应机理进行了计算分析，对反应过程中的反应物、中间体、过渡态及产物进行了全几何参数优化，得到其构型和基本参数。对得到的中间体和过渡态进行频率分析和内禀反应坐标(IRC)计算，以证实中间体和过渡态的正确性和相互连接关系。使用QCISD方法在6-311G(d, p)基组水平对各驻点的单点能进行计算，给出能量信息。计算结果表明：CaH2与NH3主要以摩尔比为1:2进行反应，分两步氢取代过程，生成产物Ca(NH2)2和2H2。反应所释放的H2中两个H原子分别来源于CaH2和NH3，反应的关键是脱氢，主要在于克服N―H键断裂所需能量。相比较而言从NH3中脱氢比从―NH2中脱氢较易。
The reaction mechanism between NH3 and CaH2 has been investigated by a B3LYP method of density functional theory at the 6-311G(d,p) level, and the geometries of reactants, intermediates, transition states and products have been calculated. Vibration analysis and intrinsic reaction coordinates (IRC) calculation at the same level have been applied to validate the connection of the stationary points. The single point energy of each station is calculated using the QCISD method at the 6-311G (d, p) level, to get the energy information.The results indicate that the reaction between NH3 and CaH2 is mainly reacted at a molar ratio of 1:2 and has two hydrogen substitution reactions with the reaction products Ca(NH2)2 and H2. The two released hydrogen atoms in H2 come from NH3 and CaH2 respectively. The sticking point of the dehydrogenation is overcome to break the bond of N-H. In contrast, dehydrogenation from NH3 is easier to dehydrogenate from -NH2.