Ab initio Study of the Cl_2O_3 Isomers and Their Role in the ClO + OClO Reaction

摘要

The mechanism for the reaction ClO + OClO has been investigated by ab initio molecular orbital and transition state theory calculations. Nine stable isomers of Cl_2O_3 (including optical isomers) are located at the B3LYP/6-311+G(3df) level and their energies are refined by the modified Gaussian-2 (G2M) method. The formation of ClOCl(O)O is dominant at low temperatures, taking place barrierlessly with the second and third order rate constant, (k_1)~∞ = 3.0 × 10~(-10) cm~3 molecule~(-1) s~(-1) and (k_1)~0 = 1.1 × 10~(-17) T~(-5.5) exp (-398/T) cm~6 molecule~(-2) s~(-1) in the temperature range of 200 - 400 K for N_2 as the third-body. For ammonium perchlorate combustion applications, we have predicted the rate constants for the products of ClOO + ClO and ClOCl + ~1O_2. Their overall rate constants can be given by: k_(ClOO) = 1.0 × 10~(-22) T~(2.8) exp(- 78/T) and k_(ClOCl) = 9.6 × 10~(-22) T~(2.4) exp(-1670/T)cm~3 molecule~(-1) s~(-1), respectively, in the temperature range of 500 - 2500 K.