Sergeev Oleg V, Yanilkin Alexey V
Center for Fundamental and Applied Research, Dukhov Research Institute of Automatics , P.O. Box 918, Moscow 101000, Russia.
Department of Molecular and Chemical Physics, Moscow Insitute of Physics and Technology , Moscow, Russia.
J Phys Chem A. 2017 Apr 27;121(16):3019-3027. doi: 10.1021/acs.jpca.6b13088. Epub 2017 Apr 12.
Energetic materials are characterized by fast and complex chemical reactions. It makes them hardly available for kinetic experiments in relevant conditions and a good target for reactive molecular dynamics simulations. In this work, unimolecular and condensed-phase thermal decomposition of pentaerythritol tetranitrate (PETN) are investigated by ReaxFF molecular dynamics. It is shown that the decomposition kinetics in condensed phase may be described with the activation barrier lower by a factor of 2 than that for isolated molecules. The effect of the intermolecular hydrogen transfer is revealed in condensed phase. Energetic barriers for hydrogen transfer in two energetic materials (methyl nitrate, which is a nitroester as well as PETN, and o-nitrotoluene) are studied with ReaxFF and DFT using nudged elastic band technique. The results indicate that ReaxFF gives significantly lower activation energy for intermolecular hydrogen transfer in nitroesters than different DFT approximations, which explains the molecular dynamics results for PETN.
含能材料的特点是化学反应快速且复杂。这使得它们在相关条件下难以用于动力学实验，却是反应分子动力学模拟的良好对象。在这项工作中，采用反应力场（ReaxFF）分子动力学方法研究了季戊四醇四硝酸酯（PETN）的单分子和凝聚相热分解。结果表明，凝聚相中的分解动力学可以用比孤立分子低2倍的活化能垒来描述。揭示了凝聚相中分子间氢转移的影响。使用推挤弹性带技术，通过ReaxFF和密度泛函理论（DFT）研究了两种含能材料（硝酸甲酯，它是一种硝酸酯以及PETN，和邻硝基甲苯）中氢转移的能垒。结果表明，与不同的DFT近似方法相比，ReaxFF给出的硝酸酯分子间氢转移活化能显著更低，这解释了PETN的分子动力学结果。
