气相中~2Sr^+,~2Ba^+介入N_2O与H_2反应的理论研究

Theoreticalstudy for the reaction of N_2O with H_2 mediated by ~2Sr^+ and ~2Ba^+ in the gas

运用密度泛函理论DFT-UB3LYP方法,对2Sr+、2Ba+采用相对论校正赝势基组SDD,对N、O、H采用6-311+G(2d,p)基组,计算研究了气相中碱土金属离子2Sr+、2Ba+介入N2O(1∑+)和H2(1∑g+)反应的微观机理,优化了二重态势能面上各反应物、中间体和过渡态的构型特征,用频率分析方法和内禀反应坐标方法(IRC)对过渡态进行了验证.运用Kozuch撰写的能量跨度模型(Energetic Span Model,δlE),确定了决定循环反应速率的决速过渡态(TDTS)和决速中间体(TDI),并利用转化频率(Turnover Fre-quency,TOF)评估了催化性能.结果表明:从热力学性质分析2Sr+、2Ba+离子对N2O(1∑+)和H2(1∑g+)反应很好的催化作用,可得到目标产物N2(1∑g+)和H2O(1 A1),却从动力学性质分析主要反应产物为N2、SrOH+(BaOH+)和H,最终动力学因素在反应中起决定性作用,以上结论与实验观测结果相符.

The mechanism of the reaction of N2O （1 ∑＋ ） and H2 （1∑＋ ） mediated by cations Sr＋ and Ba＋ has been investigated by using the UB3LYP density functional theory （DFT） with the relativistic effec- tive core potential （RECP） of basis sets （SDD） for 2Sr＋ ,2Ba＋ and the 6-311＋G（2d,p） basis set for N, O and H on doublet energy surfaces. The geometries for reactants, the transition states and the products are completely optimized. All the transition states are verified by the vibrational analysis and the internal reaction coordinate （IRC） calculations. The energetic span （δE） model coined by Kozuch was applied in this cycle to obtain some kinetic information. TDTS and the TDI were confirmed, and the TOF （E-rep- resentation） was calculated by the AUTOF program. Considering thermodynamic factor, the Sr＋ and Ba＋ have good catalytic function for the reaction of N2O （X1∑＋） ＋ H2（1∑g＋）→ N2（l∑g＋） ＋ H2O （1 A1）, but on the kinetics, the products are N2 ,SrOH＋ （BaOH＋） and H. Finally, the decisive role of ti- tle reaction is the kinetic aspect, our calculated results are in close agreement with observations.