Molecular Dynamics Simulations of Femtosecond Laser Ablation of Energetic Materials

Abstract

To understand the physical and chemical responses of energetic materials, such as 1,3dinitrobenzene (DNB, C6H4N2O4), hexanitrohexaazaisowurtzitane (CL20, C6H6N12O12), and CL20/DNB co-crystal, to femtosecond laser ablation (FLA), their molecular reaction dynamics have been investigated using the ReaxFF/ lg force field. The computational results indicate that the temperature and pressure of the CL20/DNB system jump during FLA. In particular, the temperature and pressure gradually reach their maxima following an initial cooling process. N-NO2 bond breaking of the CL20 molecule triggers the reactions for both the CL20 and CL20/ DNB systems. However, the CL20 system prevails the CL20/DNB co-crystal in the decomposition rate simply because coexistence of DNB molecules in the mixture and generated decomposition products containing benzene rings greatly reduce the effective collision probability between CL20 and the products.

Microscopic Mechanisms of Femtosecond Laser Ablation of HMX from Reactive Molecular Dynamics Simulations

“…27−32 However, there are fewer free electrons in explosives than in metal materials; the singletemperature model is mainly used in the energy coupling between fs-laser pulses and explosives. In 2016, Yang et al 33 performed MD calculations on fs-laser ablations of explosives, including 1,3-dinitrobenzene (DNB), CL-20, and CL-20/DNB cocrystals. By use of the single-temperature model, the main products and the initial decomposition pathways of explosives irradiated by fs-lasers were obtained.…”

“…Under fs-laser irradiation, the free electrons are the earliest to be excited and then transfer energy to their surrounding lattice by radiating longitudinal optical (LO) phonons outward; thus, the TTM model is more suitable than the single-temperature model for calculating the laser ablation of metals. − However, there are fewer free electrons in explosives than in metal materials; the single-temperature model is mainly used in the energy coupling between fs-laser pulses and explosives. In 2016, Yang et al . performed MD calculations on fs-laser ablations of explosives, including 1,3-dinitrobenzene (DNB), CL-20, and CL-20/DNB cocrystals.…”