Strachan Alejandro, Kober Edward M, van Duin Adri C T, Oxgaard Jonas, Goddard William A
Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
J Chem Phys. 2005 Feb 1;122(5):54502. doi: 10.1063/1.1831277.
We use the recently developed reactive force field ReaxFF with molecular dynamics to study thermal induced chemistry in RDX [cyclic-CH(2)N(NO(2))] at various temperatures and densities. We find that the time evolution of the potential energy can be described reasonably well with a single exponential function from which we obtain an overall characteristic time of decomposition that increases with decreasing density and shows an Arrhenius temperature dependence. These characteristic timescales are in reasonable quantitative agreement with experimental measurements in a similar energetic material, HMX [cyclic-CH(2)N(NO(2))]. Our simulations show that the equilibrium population of CO and CO(2) (as well as their time evolution) depend strongly of density: at low density almost all carbon atoms form CO molecules; as the density increases larger aggregates of carbon appear leading to a C deficient gas phase and the appearance of CO(2) molecules. The equilibrium populations of N(2) and H(2)O are more insensitive with respect to density and form in the early stages of the decomposition process with similar timescales.
我们使用最近开发的反应力场ReaxFF结合分子动力学方法，研究了不同温度和密度下RDX[环-（CH₂N(NO₂)）₃]中的热致化学反应。我们发现，势能的时间演化可以用单一指数函数较好地描述，由此我们得到了一个整体的分解特征时间，它随密度降低而增加，并呈现出阿仑尼乌斯温度依赖性。这些特征时间尺度与类似含能材料HMX[环-（CH₂N(NO₂)）₄]的实验测量结果在合理的定量上相符。我们的模拟表明，CO和CO₂的平衡丰度（以及它们的时间演化）强烈依赖于密度：在低密度下，几乎所有碳原子都形成CO分子；随着密度增加，出现了更大的碳聚集体，导致气相中碳不足，并出现了CO₂分子。N₂和H₂O的平衡丰度对密度不太敏感，且在分解过程的早期阶段以相似的时间尺度形成。
