Molecular dynamic simulation for thermal decomposition of RDX with nano-AlH3 particles

Abstract

Molecular dynamic simulation of a high explosive, RDX, mixed with AlH₃ nanoparticles was performed by a newly parameterized ReaxFF force field. Testing of the ReaxFF shows that the mean absolute errors of the densities and bond lengths between calculated and experimental values are less than 7% and 3%, respectively. Using the ReaxFF, effects of AlH₃ nanoparticles with different radii on the thermal decomposition of RDX were revealed. A new mechanism of the generation and the consumption of H₂ was discovered in the explosion. The H₂ is released by AlH₃ firstly and then it reacts with NO₂ and CO₂ from the decomposition of RDX, leading to an increase of H₂O, NO and CO. Meanwhile, the size effect of AlH₃ upon the reaction was also revealed. As a result, the number of produced H₂O and CO₂ molecules increases by 10.38% and 56.85%, respectively, when the radius of AlH₃ nanoparticles decreases from 1.10 to 0.68 nm. This showed that RDX decomposes more completely with smaller AlH₃ nanoparticles, which was further demonstrated by the analysis of reaction residues and diffusion coefficients.