Effects of hot spot distance on explosive ignition and reaction growth : A reactive molecular dynamics simulation study

Hot spots resulted from shock-induced void collapse could seriously alter the ignition and initial chemical reactions in heterogeneous explosive crystals. Herein, the influences of hot spot distance on ignition and reaction growth in the crystalline RDX were investigated through reactive molecular dynamics simulations. As two voids collapsed completely, double hot spots occurred at the internal upstream and downstream voids in the crystalline RDX, respectively. The farther hot spot distance could be observed in the bulk RDX with the larger void-void distance. Combined with the resulted chemical fragments analysis, hot spot distance affects the chemical reaction rate but does not alter the initial decomposition mechanism in RDX. The farther hot spot distance results in a faster decomposition degree of RDX molecules, a higher concentration of NO₂ liberation, and even greater violent growth for explosive reaction. It is evident that RDX with a longer void-void distance is more sensitive to the present overdriven shock. The farther double hot spots result in more RDX molecules being heated simultaneously and then reacted quickly under the synergetic growth of double hot spots. In terms of the synergetic growth of double hot spots, it is demonstrated that reducing hot spot distance could result in decreasing the high-temperature area ratio in the crystalline RDX exposed to an overdriven insult, avoiding the occurrence of a greater violent scenario. The present study can provide an efficient route to understand the role of hot spot distance in ignition and reaction growth and further evaluate the shock sensitivity of crystalline explosives.