飞秒激光烧蚀黑索今的分子动力学模拟  

Reactive Molecular Dynamics Simulation of Microscopic Mechanisms of Femtosecond Laser Ablation of RDX

作　　者：伍俊英[1] 杨利军 李姚江 陈朗[1] WU Junying;YANG Lijun;LI Yaojiang;CHEN Lang(State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081, China)

机构地区：[1]北京理工大学爆炸科学与技术国家重点实验室,北京100081

出　　处：《兵工学报》2021年第1期214-224,共11页Acta Armamentarii

基　　金：爆炸科学与技术国家重点实验室开放基金项目(KFJJ20-04M)。

摘　　要：利用飞秒激光的超短脉冲时间和超高能量密度的特点,可以实现对炸药的精密加工和纳米含能材料的制备。深入认识飞秒激光烧蚀炸药机理是发展飞秒激光加工技术的基础。采用反应分子动力学方法,基于ReaxFF/lg反应力场,对不同飞秒激光能量作用黑索今(RDX)过程进行分子动力学模拟,分析RDX初始分解反应路径、粒子扩散逃逸特征,研究不同飞秒激光能量作用下RDX的烧蚀机制。结果表明:在不同飞秒激光能量作用下,RDX的烧蚀机制不同。当激光能量较高时(激光能量1.0 mJ/pulse,激光能量密度51 J/cm^(2)),RDX瞬间发生分解反应,产生高温高压等离子体,产物中有大量的单原子、离子以及小分子产物;当激光能量较低时(激光能量0.2 mJ/pulse,激光能量密度10.2 J/cm^(2)),RDX主要以完整分子形式气化扩散逃逸,炸药以光机械烧蚀机制去除;在飞秒激光烧蚀炸药过程中,逃逸的粒子速度极高,粒子难以向未烧蚀区域传递能量,不会引发热扩散效应,因此能够实现对炸药的冷加工。The femtosecond laser can be used for the precise machining of explosives and the preparation of energetic nanomaterials because of its ultra-short pulse duration and ultra-high energy density.Deep understanding of the femtosecond laser ablation mechanism of energetic materials is the basis for rational use of femtosecond laser machining technology.The molecular dynamics calculations of RDX ablated by femtosecond laser were conducted based on ReaxFF/lg reactive force field.The decomposition reaction pathway and particle diffusion of RDX were analyzed,and the ablation mechanism of RDX under different femtosecond laser energies was discussed.Results show that the ablation mechanisms of RDX are different under the action of different femtosecond laser energies.When the laser energy is high enough(e.g.,1.0 mJ/pulse,51 J/cm^(2)),RDX is rapidly decomposed to generate high-temperature and high-pressure plasma.In addition,there are many single atoms,ions and small molecular fragments in the products;when the laser energy is relatively low(e.g.,0.2 mJ/pulse,10.2 J/cm^(2)),the explosive is removed by a photomechanical ablation mechanism,RDX in laser focal zone escapes as its starting molecular structure.During the femtosecond laser ablation,the high-speed particles in focal zone quickly escape outward and become difficult to transfer the energy to the surroundings,by which the explosive can be removed effectively without causing thermal diffusion.Therefore,the“cold”machining of explosives can be realized.

关 键 词：黑索今 分子动力学 飞秒激光 ReaxFF/lg反应力场 

分 类 号：TQ564.3[化学工程—炸药化工] TJ55[兵器科学与技术—军事化学与烟火技术]