摘要
本文用SCF ab initio方法对插入反应SiH_2(~1A_1)+H_2→SiH_4的反应物、产物及过渡态,在3-21G基组下优化出了它们的几何构型,并计算了该构型下的频率,进而计算了该反应的热焓△H。自由能AG和平衡常数K_D,计算结果指出在1500K以下该反应是放热的,能自发进行,然后,用Eyring过渡态理论计算了该反应的速度常数k(T),其值与Inoue的实验结果符合得很好。
In This paper, SCF ab intio method was used to treat the reactants, product and transition state of insertion reaction ('A_1) SiH_2 + H_2→ SiH_4. The configurations of each species were optimized with 3-21G basis set, and the vibrational frequencies for the configuration were cal- culated. Then the transition state entropy change △S~≠ and reaction rate constant kT was cal- culated with Eyring transition state theory. The negative △S~≠ means the reaction pass through a tight transition state. The rate constant value k (298K) = 6.2357 × 10^(-15) lmol^(-1)s^(-1) is in good agree- ment with the experimental result by Inoue k (298K) = (1.0 0.4) × 10^(-16) lmol^(-1)s^(-1). Finally the enthalpy △ H, free enrgy △ Gand the equilibrium constant K (T) of this reaction were calcu- lated, and we point out that this reaction is exo-thermal and can go on spontancously. We also corrected all above kinetic and thermodynamic quantities with frequency correction and zero-point energy correction. After correction the theoretical reaction rate constant k (298K) = 3.9799 × 10^(-17) lmo1^-s^(-1) is in better agreement with the experimental result than before.
