飞秒激光作用TATB的大尺寸分子动力学模拟

doi:10.12382/bgxb.2023.0196

摘要/Abstract

摘要：

深入认识炸药在飞秒激光作用下的快速化学反应机制和热力响应特征,是发展飞秒激光加工炸药技术的基础。采用分子动力学方法,基于ReaxFF/lg反应力场,对不同飞秒激光能量作用于三氨基三硝基苯(TATB)炸药的过程进行亚微米级大尺寸反应分子动力学模拟,考虑炸药对飞秒激光的非线性吸收过程,分析炸药烧蚀去除机制、产物演化和热力响应规律。计算结果表明:不同强度的飞秒激光对TATB的烧蚀去除机制不同,当激光强度为6.79×10¹⁷W/m²时,TATB发生等离子体烧蚀,产物以小分子或等离子体为主;当激光强度为3.39×10¹⁷W/m²时,TATB发生不完全反应,产物以大分子或团簇为主;当激光强度为1.69×10¹⁷W/m²时,TATB发生光机械烧蚀,以完整分子形式被剥离去除;激光强度越高,烧蚀产物的温度和粒子速度越高,对烧蚀区周围的热力响应越严重,有引发点火的风险。

关键词: 三氨基三硝基苯, 飞秒激光, 分子动力学计算, ReaxFF/lg反应力场

Abstract:

A deeper understanding of the rapid chemical reaction mechanism and thermal response characteristics of explosivessubjected to femtosecond laser pulseablation is the basis for the development of femtosecond laser machining technology forexplosives. The large-scale reactive molecular dynamics simulations of 1,3,5-Triamino-2,4,6-trinitrobenzene (TATB)subjected to different femtosecond laser energiesare carried out based on ReaxFF/lg reaction force field. The non-linear absorption process of explosives to femtosecond laser pulse is considered, and the ablation mechanism, product evolution and thermal response of explosives are analyzed. The calculation results show that the ablation mechanisms of TATB are different underthe action ofdifferent intensity femtosecond lasers. When the laser intensity is 6.79×10¹⁷W/m², TATB is subjected toa plasma ablation, and the products are mainly small molecules. When the laser intensity is 3.39×10¹⁷W/m², TATB undergoes an incomplete reaction, and the products are mainly large molecules or clusters. When the laser intensity is 11.69×10¹⁷W/m², TATB is subjected to a photomechanical ablation, andthe explosives are removed in an intact original molecular structure. The higher the laser intensity is, the higher the temperature and particle velocity of ablation products are, and the more severe the thermal response around the ablation zone is, which could trigger the risk of ignition.

Key words: 1,3,5-triamino-2,4,6-trinitrobenzene, femtosecond laser, molecular dynamics calculation, ReaxFF/lgreaction force field

中图分类号:

TJ55

伍俊英, 李钧剑, 尚伊平, 杨利军, 陈朗. 飞秒激光作用TATB的大尺寸分子动力学模拟[J]. 兵工学报, 2024, 45(7): 2351-2363.

WU Junying, LI Junjian, SHANG Yiping, YANG Lijun, CHEN Lang. Large-scale Molecular Dynamics Simulation of Femtosecond Laser Pulse Ablation on TATB[J]. Acta Armamentarii, 2024, 45(7): 2351-2363.

图/表 16

图1 分子动力学计算模型示意图

Fig.1 Schematic diagram of molecular dynamics calculation model

图2 飞秒激光强度在TATB内的衰减曲线

Fig.2 Attenuation curves of femtosecond laser intensity in TATB

图3 飞秒激光能量加载区域的划分示意图

Fig.3 Schematic diagram of the division of femtosecond laser energy loading areas

图4 TATB烧蚀区域的局部原子快照(200μJ/pulse)

Fig.4 Local atomic snapshots of TATB ablation region(200μJ/pulse)

图5 TATB烧蚀区域的局部原子快照(100μJ/pulse)

Fig.5 Local atomic snapshots of TATB ablation region(100μJ/pulse)

图6 TATB烧蚀区域的局部原子快照(50μJ/pulse)

Fig.6 Local atomic snapshots of TATB ablation region (50μJ/pulse)

图7 不同激光能量下,主要物种数量随时间变化曲线

Fig.7 The number of major species over time under different laser energies

图8 在200μJ/pulse的激光能量作用下计算体系的粒子扩散云图

Fig.8 Particle diffusion cloud diagrams of computational system at 80ps under laser energy of 200μJ/pulse

图9 在100μJ/pulse、50μJ/pulse的激光能量作用下计算体系在80ps时的粒子扩散云图

Fig.9 Particle diffusion clouddiagrams of computational system at 80ps under laser energies of 100μJ/pulse and 50μJ/pulse

图10 不同激光能量下逃逸粒子扩散距离

Fig.10 Diffusion distances of escaped particles under different laser energies

图11 计算体系的粒子速度云图(200μJ/pulse)

Fig.11 Particle velocity cloud diagramsof computational system (200μJ/pulse)

图12 不同激光能量下冲击波阵面位置随时间变化关系

Fig.12 The position of shock wave frontover time under different laser energies

图13 计算体系的温度分布云图(200μJ/pulse)

Fig.13 Temperature distribution cloud diagramsof computational system (200μJ/pulse)

图14 计算体系的压力分布云图(200μJ/pulse)

Fig.14 Pressure distribution cloud diagrams of computational system (200μJ/pulse)

图15 计算区域的划分示意图

Fig.15 Schematic diagram of the division of calculation region

图16 不同激光能量下烧蚀区域和未烧蚀区域内的平均压力随时间变化曲线

Fig.16 Mean pressureover time in the ablated and unablated regions under different laser energies

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