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Published July 13, 2017 | Supplemental Material + Accepted Version
Journal Article Open

Thermodynamic Simulation of the RDX-Aluminum Interface Using ReaxFF Molecular Dynamics

Abstract

We use reactive molecular dynamics (RMD) simulations to study the interface between cyclotrimethylene trinitramine (RDX) and aluminum (Al) with different oxide layers to elucidate the effect of nanosized Al on thermal decomposition of RDX. A published ReaxFF force field for C/H/N/O elements was retrained to incorporate Al interactions and then used in RMD simulations to characterize compound energetic materials. We find that the predicted adsorption energies for RDX on the Al(111) surface and the apparent activation energies of RDX and RDX/Al are in agreement with ab initio calculations. The Al(111) surface-assisted decomposition of RDX occurs spontaneously without potential barriers, but the decomposition rate becomes slow when compared with that for RDX powder. We also find that the Al(111) surface with an oxide layer (Al oxide) slightly increases the potential barriers for decomposition of RDX molecules, while α-Al_2O_3(0001) retards thermal decomposition of RDX, due to the changes in thermal decomposition kinetics. The most likely mechanism for the thermal decomposition of RDX powder is described by the Avrami–Erofeev equation, with n = 3/4, as random nucleation and subsequent growth model. Although the decomposition mechanism of RDX molecules in the RDX/Al matrix complies with three-dimensional diffusion, Jander's equation for RDX(210)/Al oxide and the Zhuralev–Lesokin–Tempelman (Z-L-T) equation for RDX(210)/Al_2O_3(0001) provide a more accurate description. We conclude that the origin of these differences in dynamic behavior is due to the variations in the oxide layer morphologies.

Additional Information

© 2017 American Chemical Society. Received: April 1, 2017; Revised: June 13, 2017; Published: June 13, 2017. We thank Dr. Jianjiang Hu for many useful discussion and careful revision of the whole manuscript. We acknowledge funding support from WEP under Contract 6140656020205. Computations in this work were carried out in the Supercomputer Center of the fourth academy of CASC, P. R. China. The authors declare no competing financial interests.

Attached Files

Accepted Version - acs_2Ejpcc_2E7b03108.pdf

Supplemental Material - jp7b03108_si_001.pdf

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