Fritz Haber Research Center for Molecular Dynamics, Hebrew University, Jerusalem 91904, Israel.
J Phys Chem A. 2011 Sep 15;115(36):10181-202. doi: 10.1021/jp202059v. Epub 2011 Aug 24.
The decomposition mechanism of hot liquid nitromethane at various compressions was studied using reactive force field (ReaxFF) molecular dynamics simulations. A competition between two different initial thermal decomposition schemes is observed, depending on compression. At low densities, unimolecular C-N bond cleavage is the dominant route, producing CH(3) and NO(2) fragments. As density and pressure rise approaching the Chapman-Jouget detonation conditions (∼30% compression, >2500 K) the dominant mechanism switches to the formation of the CH(3)NO fragment via H-transfer and/or N-O bond rupture. The change in the decomposition mechanism of hot liquid NM leads to a different kinetic and energetic behavior, as well as products distribution. The calculated density dependence of the enthalpy change correlates with the change in initial decomposition reaction mechanism. It can be used as a convenient and useful global parameter for the detection of reaction dynamics. Atomic averaged local diffusion coefficients are shown to be sensitive to the reactions dynamics, and can be used to distinguish between time periods where chemical reactions occur and diffusion-dominated, nonreactive time periods.
使用反应力场（ReaxFF）分子动力学模拟研究了不同压力下热液态硝甲烷的分解机制。观察到两种不同初始热分解方案之间存在竞争，这取决于压力。在低密度下，单分子 C-N 键的断裂是主要途径，生成 CH(3) 和 NO(2) 片段。随着密度和压力升高，接近 Chapman-Jouget 爆轰条件（约 30%的压缩，>2500 K）时，主要机制转变为通过 H 转移和/或 N-O 键断裂形成 CH(3)NO 片段。热液态 NM 分解机制的变化导致了不同的动力学和能量行为以及产物分布。计算得出的焓变与初始分解反应机制的变化相关，这可以用作检测反应动力学的方便且有用的全局参数。原子平均局部扩散系数对反应动力学敏感，可用于区分发生化学反应和扩散主导、非反应时间段。
