Initial mechanisms for the decomposition of electronically excited energetic salts: TKX-50 and MAD-X1.
Initial mechanisms for the decomposition of electronically excited energetic salts: TKX-50 and MAD-X1.
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DOI：
10.1021/jp510995z
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发表时间：
2015-03
期刊：
影响因子：
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通讯作者：
Bing Yuan;Zijun Yu;E. Bernstein
中科院分区：
文献类型：
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作者：
Bing Yuan;Zijun Yu;E. Bernstein
研究了能盐TKX-50和MAD-X1（分别为二羟铵5,5′-双六唑-1,1′-二酸盐和二羟铵3,3′-二硝基-5,5′-双-1,2,4-三唑-1,1′-二醇盐）在电子态激发下的分解过程。NO和N2分子是两种材料在紫外激发后的初始分解产物。观察到NO产物为旋转冷态（1500 K）。TKX-50的NO产物振动温度为（2600±250）K，比MAD-X1高（1100±250）K。两种物质的N2产物均为旋转冷态（<30 K）。在完全主动空间自洽场（CASSCF）水平上探讨了这两种电子激发盐的初始分解机制。在CASSCF(8,8)/6-31G(d)水平上的势能面计算表明，圆锥相交在分解机制中起着至关重要的作用。电子激发的S1分子可以通过（S1/S0）CI锥形交点非绝热弛豫到低电子态。TKX-50和MAD-X1在S1态和S0态之间都有两个（S1/S0）CI锥形交点，这两个交点关联并导致了两种不同的反应路径，生成N2和NO产物。通过打开TKX-50和MAD-X1的四唑环或三唑环释放N2产物。TKX-50的胺n -氧化物部分释放NO产物，而MAD-X1则通过硝基-亚硝酸盐异构化产生NO产物。观察到的NO和N2产物的旋转能分布与每个分子在其S0势能表面上各自过渡态的最终结构一致。
Decomposition of energetic salts TKX-50 and MAD-X1 (dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate and dihydroxylammonium 3,3'-dinitro-5,5'-bis-1,2,4-triazole-1,1'-diol, respectively), following electronic state excitation, is investigated both experimentally and theoretically. The NO and N2 molecules are observed as initial decomposition products from the two materials subsequent to UV excitation. Observed NO products are rotationally cold (1500 K). The vibrational temperature of the NO product from TKX-50 is (2600 ± 250) K, (1100 ± 250) K hotter than that produced from MAD-X1. Observed N2 products of these two species are both rotationally cold (<30 K). Initial decomposition mechanisms for these two electronically excited salts are explored at the complete active space self-consistent field (CASSCF) level. Potential energy surface calculations at the CASSCF(8,8)/6-31G(d) level illustrate that conical intersections play an essential role in the decomposition mechanisms. Electronically excited S1 molecules can nonadiabatically relax to the lower electronic state through (S1/S0)CI conical intersections. Both TKX-50 and MAD-X1 have two (S1/S0)CI conical intersections between S1 and S0 states, related to and leading to two different reaction paths, forming N2 and NO products. N2 products are released by the opening of the tetrazole or triazole rings of TKX-50 and MAD-X1. NO products are released from the amine N-oxide moiety of TKX-50, and for MAD-X1, they are produced through nitro-nitrite isomerizations. The observed rotational energy distributions for NO and N2 products are consistent with the final structures of the respective transition states for each molecule on its S0 potential energy surface.