MOLECULAR DYNAMICS SIMULATIONS OF HIGH VELOCITY SHOCK COMPRESSED TNT
-
摘要: 采用反应力场分子动力学方法模拟了梯恩梯(2,4,6-trinitrotoluene,TNT) 冲击压缩过程. 冲击压缩完全时,体积压缩至原体积40%,梯恩梯分子分解完毕,体系压力达到峰值. 随后稀疏波反向拉伸致大量原子或分子基团飞溅至下游,同时压力开始卸载. 密度及粒子速度剖面显示压缩波后方密度较大,粒子基本处于静止状态,且压缩波内存在较大的粒子速度梯度. 早期化学反应特征是梯恩梯分子在冲击压缩作用下脱落H,O 原子后残基快速聚合形成较大的分子团簇,此阶段和平动—振动弛豫过程相关,并且分子由平动—振动模态转换的时间尺度为0.5 ps. 产物识别分析显示梯恩梯在高速冲击压缩下致C—H,O=N 键断裂,脱落的原子部分形成OH,H2,H2O,N2,部分H,O 原子游离在体系中. 含碳团簇分析显示,冲击压缩作用致体系中含碳团簇的摩尔质量逐渐累积. 体系内含碳团簇中O/C,H/C,N/C 原子数量比值逐渐趋于平衡(O/C=0.680,H/C=0.410,N/C=0.284),且均小于初始结构中的比值.Abstract: We simulate the shock compression behavior of TNT with ReaxFF-MD. When shock compression is complete, all of the TNT molecules are decomposed, and when volume compression is up to the 40% of original volume, pressure of the system reaches a peak. Close behind is rarefaction wave reverse stretching the compressed energetic materials and leading to a large number of atoms or molecules group splash to the downstream, pressure begin to unload at the same time. Density and particle wave velocity profile show a greater density in the compressed region, and the particles in a stationary state, but sharp velocity gradient in the region of compression wave. In the earlier chemical characteristics, TNT molecules shed the H, O atoms under the effect of shock compression, and then the residues aggregate to the larger clusters, and this phase associated with translational-vibrational relaxation processes. The rotational mode is subsequently transferred into vibrational modes with a time scale of 0.5 ps. Fragment analysis shows that a large number of C—H, O=N bonds rupture to form the OH, H2, H2O, N2 groups and parts of H, O atoms are free in the system. The molar mass of the carbon-containing clusters under the joint actions of compressional wave ahead and rear compression is accumulating gradually from the analysis. Atomic ratio in the carbon-containing clusters tends to balance (O/C=0.680, H/C=0.410, N/C=0.284), but less than the ratio in the initial structure.
-
Key words:
- shock compression /
- TNT /
- reactive force field /
- molecular dynamics
-
Van Duin ACT, Dasgupta S, Lorant F, et al. ReaxFF: a reactive force field for hydrocarbons. J Phys Chem A, 2001, 105(41): 9396-9409 Strachan A, Kober EM, van Duin ACT, et al. Thermal decomposition of RDX from reactive molecular dynamics. J Chem Phys , 2005, 122: 054502 Agrawalla S, van Duin ACT. Development and application of a ReaxFF reactive force field for hydrogen combustion. J Phys Chem A, 2011, 115(6): 960-972 Nomura K, Kalia RK, Nakano A, et al. Dynamic transition in the structure of an energetic crystal during chemical reactions at shock front prior to detonation. Phys Rev Lett , 2007, 99: 148303 Liu LC, Liu Y, Zybin SV, et al. ReaxFF-lg: correction of the ReaxFF reactive force field for london dispersion, with applications to the equations of state for energetic materials. J Phys Chem A, 2011, 115(40): 11016-11022 Wen YS, Xue XG, Zhou XQ, et al. Twin induced sensitivity enhancement of hmx versus shock: a molecular reactive force field simulation. J Phys Chem C , 2013, 117: 24368-24374 Plimpton S. Fast parallel algorithms for short-range molecular dynamics. J Comp Phys 1995, 117(1): 1-19 http://lammps.sandia.gov. Dremin AN. Shock discontinuity zone effect: the main factor in the explosive decomposition detonation process. Philosophical Transactions of the Royal Society of London. Series A: Physical and Engineering Sciences, 1992, 339(1654): 355-364 -

计量
- 文章访问数: 1426
- HTML全文浏览量: 47
- PDF下载量: 2902
- 被引次数: 0