CPMD investigation of α-RDX and ε-CL-20: the transition of deflagration to detonation depending on the self-produced radicals

Abstract

1,3,5-Trinitroperhydro-1,3,5-triazine (RDX) and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) are the classic high energy nitramine compounds. Herein, we performed simulations of the overall decomposition pathways of condensed α-RDX and ε-CL-20 by applying the Car–Parrinello molecular dynamics (CPMD) method. Both of them appear to have similar distinct initial decomposition pathways, which are the bond cleavages of N–NO₂ bonds. Interestingly, we find that the continuous explosion is nonspontaneous without the participation of self-produced hydrogen radicals of RDX or oxygen radicals of CL-20. Increased radicals are produced gradually with increasing temperature, which activates further entropy-increased steps, resulting in the uncontrollable transition of deflagration to detonation with the formation of NO_x, CO_x and HCN. Herein, we provide a detailed and systematic description of the decomposition for unit-cell α-RDX and ε-CL-20 under increased temperature, which can be summarized as C₃H₆O₆N₆ (RDX) → NO + HNO + H₂ + CO₂ + HCHO + HNCN + N₂O and C₆H₆O₁₂N₁₂ (CL-20) → NO + HONO + 5HCN + CO₂ + N₂O + 3NO₂.