Large-scale Molecular Dynamics Simulation of Femtosecond Laser Pulse Ablation on TATB

doi:10.12382/bgxb.2023.0196

Abstract

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

CLC Number:

TJ55

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.

Figures/Tables 16

Fig.1 Schematic diagram of molecular dynamics calculation model

Fig.2 Attenuation curves of femtosecond laser intensity in TATB

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

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

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

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

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

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

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

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

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

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

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

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

Fig.15 Schematic diagram of the division of calculation region

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

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