Simulation investigations in the binding energy and mechanical properties of HMX-based polymer-bonded explosives

The molecular simulations of the well-known high explosive beta-HMX (cyclotetramethylene tetranitramine) and its fluorine containing polymer-bonded explosives (PBXs) were carried out with the combination method of quantum mechanics, molecular mechanics and molecular dynamics. The atomic cluster model, containing the beta-HMX molecule and the polymer molecule whose chain dimension was about the same as beta-HMX's, was fully optimized by AM1 and PM3 semi-empirical molecular orbital and molecular mechanical methods using COMPASS and PCFF force field. Then the calculated binding energy is found to be linearly correlated to each other. Molecular dynamics simulations using COMPASS force field were performed for beta-HMX crystal and the PBXs involving beta-HMX and a series of fluorine containing polymers. Their elastic coefficients, moduli and Poisson's ratios were calculated. It is found that the mechanical properties of beta-HMX can be effectively improved by blending with fluorine containing polymers in small amounts.