Chemical Insight on Decreased Sensitivity of CL-20/TNT Cocrystal Revealed by ReaxFF MD Simulations.

Understanding the underlying mechanisms on sensitivity-decrease of the CL-20/TNT cocrystal is essential for wide applications of the promising high-energetic CL-20. This work presents the chemical scenario of CL-20/TNT thermolysis obtained from ReaxFF molecular dynamics simulations. Facilitated by the unique VARxMD for reaction analysis, the interplay reactions between CL-20 and TNT responsible for the sensitivity-decrease of CL-20/TNT was first revealed. The early response of CL-20/TNT to thermal stimulus is dominated by N-NO2 bond cleavage for NO2 formation and C-N bond scission leading to ring-opening of CL-20. The kinetics of N-NO2 and C-N bond cleavage, as well as the following oxygen-abstraction of NO2, are significantly slowed in the CL-20/TNT thermolysis against β-CL-20, which are responsible for the low sensitivity at the stage of active intermediate generation. The early formed active intermediates of NO2, NO3, NO, and N2O are confined and consumed by the reactions of the surrounding TNT or ring intermediates from TNT conversion, accounting for over 40% reactions of NO2 consumption. The abundant active intermediates are consumed mainly by the direct linking of active NO2 and NO with the nitro groups of TNT, hydrogen-abstraction from TNT and oxidation of benzene rings. The complex interplay reactions between TNT and the active intermediates generated significantly retard the chain-like reactions for further exothermal process, decreasing the sensitivity of CL-20/TNT. The comprehensive chemical understanding on the sensitivity-decrease of CL-20/TNT thermolysis revealed by ReaxFF MD simulations can offer assistance for tuned sensitivity of new energetic CL-20-based cocrystals.