气相中~2Ca^+介入N_2O与CO,N_2O与H_2反应的计算研究

DFT study for the reduction of N_2O and CO,N_2O and H_2 mediated by Ca^+

本文采用密度泛函理论DFT-UB3LYP方法,在6-311+G(2d)和6-311+G(2d,p)的基组下,计算研究了气相中Ca^+离子介入N_2O(~1∑^+)和CO(~1∑^+)与N_2O(~1∑^+)和H_2(~1∑_g^+)反应的微观机理.报道了二重态势能面上各反应物、中间体和过渡态的构型特征及能量,并用频率分析和内禀反应坐标(IRC)方法对过渡态进行了验证.计算结果表明,金属离子参与N_2O和CO与N_2O和H_2的反应都分两步进行,其中Ca^+离子对反应N_2O(X^1∑^+)+CO(~1∑^+)生成N_2(X^1∑_g^+)+CO_2(~1∑_g^+)比较Fe^+,Ir^+,Pt^+等的金属离子有良好的催化作用,而对反应N_2O(X^1∑^+)}H_2(~1∑_g^+)→N_2(~1∑_g^+)+H_2O(~1A_1)催化作用不是很好,N_2、CaOH^+和H是该反应的主要产物,与实验观测结果相符,并通过对金属离子亲氧性(OA)的计算,从热力学方面进一步说明主题反应的可行性.

The mechanism of the reaction N2O （1∑＋） and CO （1∑＋） with N2O （1∑＋） and H2 （1∑＋） mediated by Ca＋ has been investigated on doublet energy surfaces. The reactions are studied by using the UB3LYP density functional theory （DFT） and the standard 6-311＋G（2d） and 6-311＋G（2d,p） basis sets. 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 result shows that the reactions were proceed in two-step, in that, compare with the Fe＋ , Ir＋ and Pt＋ , the Ca＋ has good catalytic function for the reaction of N2O （X1∑＋ ）＋CO （1∑＋） →N2 （X1∑＋ ） ＋CO2 （1∑＋ ）, but no function for the reaction of N2 O （X1∑＋ ） ＋ H2 （1∑＋ ） → N2 （1∑＋ ） ＋ H20 （1A1）, the products are N2 .CaOH＋ and H. Finally, O-atom affinities （OA） testified that the conclusion is thermodynamically allowed.