Initial Response of Pentaerythritol Tetranitrate (PETN) under the Coupling Effect of Preheating, Shock and Defect via the Molecular Dynamics Simulations with the Multiscale Shock Technique Method

The initial response of PETN under the coupling of preheating, impact and defects was simulated by Multiscale Shock Technique (MSST) method and molecular dynamics. The temperature change of PETN during impact compression can be divided into three stages: (1) the elastoplastic change of the system caused by initial compression; (2) part of PETN decomposes and releases energy to raise temperature; (3) a secondary chemical reaction occurs, resulting in rapid temperature rise. Under the given conditions, a higher initial preheating temperature will lead to faster decomposition of PETN; The existence of defects will accelerate the decomposition of PETN molecules; Coupling the highest preheating temperature with defects will lead to the fastest decomposition of PETN molecules, while in the defect-free PETN system with a preheating temperature of 300 K, the decomposition of PETN molecules is the slowest. For the case of U_s = 8 km·s⁻¹, the effect of defects on the initial PETN reaction is greater than the initial preheating temperature; When the impact velocity is greater than 9 km·s⁻¹, the impact velocity is an important factor affecting the decomposition of PETN molecules. For U_s = 10 km·s⁻¹, NO₂ is the main initial product in the defective PETN crystal, while in the perfect PETN crystal, it is the combination of NO₂ and HONO. The chemical reaction kinetics analysis shows that the preheating temperature and defects will accelerate the decomposition of PETN. The higher the preheating temperature, the faster the decomposition of PETN. For the case of U_s = 7 km·s⁻¹, 8 km·s⁻¹ and 9 km·s⁻¹, the existence of defects will increase the decomposition rate by more than 50% regardless of the initial preheating temperature. In the case of Us = 10 km·s⁻¹, the improvement of decomposition rate by defects is not as significant as the initial preheating temperature.