Ab initio study of ammonium perchlorate combustion initiation processes : unimolecular decomposition of perchloric acid and the related OH z ClO 3 reaction {
نویسنده
چکیده
The unimolecular decomposition of HClO4 has been investigated at the G2M//B3LYP/6-311zG(3df, 2p) level of theory. Above 500 K, the decomposition process was found to depend strongly on pressure below 200 atm. The rate constants at the highand low-pressure limits were predicted to be k1 ‘ ~ 1.5 6 10 exp(226500/ T) s and k1 0 ~ 3.39 6 10 T exp(229430/T) cm molecule s, respectively. Under the atmosphericpressure condition, the predicted first-order rate coefficient for the temperature range 300–3000 K, k1 ~ 5.0 6 10 51 T exp(230700/T) s, agrees reasonably with experimental data obtained at 550–750 K by different experimental groups. We have also calculated the rate constants for the bimolecular reaction of OH with ClO3 producing HClO4 by association/stabilization and HO2 z ClO2 by association/fragmentation. At the high-pressure limit, the rate constants can be given as:k21 ~ 3.26 10 210 T 0.07 exp(225/T) cm molecule s and k2 ~ 2.1 6 10 210 T 0.09 exp(218/T) cm molecule1 s, respectively, for the temperature range 300–3000 K. Under the atmospheric pressure condition, the OHz ClO3 reaction produces predominately the HO2 z ClO2 products.
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