ReaxFF Molecular Dynamics Simulation of Hydrostatic and Uniaxial Compression of Nitrate Energetic Materials

Abstract

The physical and chemical properties of typical nitrate energetic materials under hydrostatic compression and uniaxial compression were studied using the ReaxFF/lg force field combined with the molecular dynamics simulation method. Under hydrostatic compression, the Pâ'V curve and the bulk modulus (B0) obtained using the VFRS equation of state show that the compressibility of the three crystals is nitroglycerine (NG) > erythritol tetranitrate (ETN) > 2,3-bis-hydroxymethyl-2,3-dinitro-1,4-butanediol tetranitrate (NEST-1). The a- A nd c-axis of ETN are easy to compress under the action of hydrostatic pressure, but the b-axis is not easy to compress. The b-axis of NEST-1 is the most compressible, while the a- A nd c-axis can be compressed slightly when the initial pressure increases and then remains unchanged afterward. The a-, b-, and c-axes of NG all have similar compressibilities. By analyzing the change trend of the main bond lengths of the crystals, it can be seen that the most stable of the three crystals is the Nâ'O bond and the largest change is in the Oâ'NO2 bond. The stability of the Câ'O bond shows that the NO3 produced by nitrates is not from the Câ'O bond fracture. Under uniaxial compression, the stress tensor component, the average principal stress, and the hydrostatic pressure have similar trends and amplitudes, indicating that the anisotropy behaviors of the three crystals ETN, NEST-1, and NG are weak. There is no significant correlation between maximum shear stress and sensitivity. The maximum shear stresses τxyand τyz of the ETN in the [010] direction are 1.5 GPa higher than τxz. However, the maximum shear stress of NG shows irregularity in different compression directions, indicating that there is no obvious correlation between the maximum shear stress and sensitivity.