Reactive molecular dynamics simulation of the thermal decomposition mechanisms of 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo[5.5.0.05,9.03,11]dodecane (TEX)

Abstract

4,10-Dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo[5.5.0.05,9.03,11]dodecane (TEX) is a new type of cage-structured explosive with good explosive performance, good thermal stability and low production cost. TEX has high application value in casting and press-packed explosives. A TEX supercell model was constructed using the reaction molecular dynamics (MD) method. Based on the ReaxFF/lg reactive force field, an MD simulation of the thermal decomposition process of TEX explosives at different temperatures (2000 K, 2500 K, 3000 K, and 3500 K) was performed. The calculations were carried out to analyze the initial reaction pathways, small molecule products, destruction of the TEX cage structure and formation of clusters. The structural characteristics and elemental composition of the clusters were studied, and the reaction kinetic parameters of TEX at different reaction stages were calculated. During the thermal decomposition process, the NNO2 bond in the TEX molecular structure breaks first, then the adjacent CO bond is stretched, and finally the cage structure is gradually destroyed. The main decomposition products are small molecules (NO2, NO, H2O, CO2, N2, H2, HNO2 and HNO) and clusters (C12H12N6O12 and C18H13N7O14). The effect of temperature on the clusters is twofold. On the one hand, when the temperature is low, the cage structure of the TEX molecule is difficult to destroy and is not conducive to cluster growth. On the other hand, when the temperature is high, clusters are generated in the TEX supercell system but are subsequently rapidly decomposed. Throughout the whole process, H, N and O will gradually escape from the cluster, but O is more confined to the cluster, which will affect the subsequent autoxidation process of TEX to some extent.