Theoretical Study And Design Of CL-20-based Composite Explosives

At present,2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(CL-20)is one of the high energy single-compound explosives,but the application of CL-20 is limited due to the poor safety performance caused by the high sensitivity.In this study,two kinds of CL-20-based composite explosives,including cocrystal and melt cast explosive,were investigated through the Molecular Dynamics(MD),quantum chemistry calculation and experimental methods.It is hoped that this paper could provide some reference value for the future researches.The main study contents and innovative results are as follows:1)A series of nitropyrazole compounds were designed according to the type,position and quantity of substituents in the pyrazole ring,then the intermolecular interactions and sensitivity of the complexes of CL-20 and nitropyrazoles were studied by quantum chemistry calculations.The interactions of the complexes were studied through Atoms in Molecules(AIM)anf Non-covalent Interaction(NCI)methods,and the interaction energy was calculated.The sensitivity of the complexes was studied using the analysis of trigger bonds and Electrostatic Potential(ESP).2)The MD,Monte Carlo(MC)method and the Universal Solvation Model(SMD)model were employed to investigate 3,4-dinitropyrazole(DNP)/CL-20 cocrystal.The influnence of molar ratios and solvents on the cocrystal were studied and the crystal structure of DNP/CL-20 was predicted.The free space in the crystal structure was uesd to study the sensitivity.The stability of DNP/CL-20 complexes in different solvents was studied.The resuts indicated that DNP/CL-20 cocrystal might formed in a molar ratio of 1:1.The stability of the cocrystal is the higher in the methanol and ethanol solvent at 308 K.Then,the detonation paramaters of the cocrystal were calculated.3)The 1-methyl-3,4,5-trinitropyrazole(MTNP)/CL-20 cocrystal was prepared in the ethanol.The crystal morphology and growth mechanism of the cocrystal in ethanol were investigaeted theoretically.The simulated crystal morpholygy of MTNP/CL-20 cocrystal agrees well with the expremental result.The cocrystal-solution model simulations show that the CL-20 and MTNP molecules are easer absorbed on the growth surfaces of the cocrystal than ethanol molecules.The cooperativity effect shows that the MTNP/CL-20 complexes turn to be more stable in the presence of ethanol.4)The melting point and formation mechanism of DNP/MTNP binary eutectic mixture were invetigated by Differential Scanning Calorimeter(DSC)test,MD simulation and quantum chemical calculations.The binary phase diagram for the DNP/MTNP system was predictd computationally and determined experimenally.The calculated eutectic temperature is 336.60 K in a mass ratio of 50:50.The DNP/MTNP complexes were optimized and the interaction energy was calculated by quantum chemistry calculation.It was found that,besides the hydrogen bonds,the role of ?-? interactions are significant in the assembly of the complex.The stability and safety performence of the eutectic were studied through the flash point,imact sensitivity,vacuum stability and compatibility tests.5)The absorption behaviors of melting ingredients with the crystal surfaces of CL-20 and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX)were investigated by MD simulations.The binding energy was calculated,and the effect of molcular arrangment and surface roughness on the absorption ability were analyzed.The results show that the absorpyion ability of melting ingredients on the surfaces is in the order MTNP > DNP > 2,4,6-Trinitrotoluene(TNT)> 2,4-Dinitroanisole(DNAN).Due to the smoother molecular arrangement of HMX surfaces,the accseeible area of carriers on the surfaces is smaller,hence,the binding energy per unit area is smaller.