| 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexazisowurtzitane(CL-20)and 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclo octane(HMX)are both high-energy single explosives,but the presence of high energy and high sensitivity has limited their further application.Cocrystal technology is widely concerned by researchers as an explosive modification method which can be used to balance the energy and sensitivity of explosives and improve the safety of explosives.In this study,the effect of solvent mixtures on the formation and crystal morphology of CL-20/HMX cocrystal explosive was investigated through Molecular Dynamics(MD)and Quantum Chemistry(QC)calculation methods.The results of this paper can provide some reference values for the future design and research of energetic materials in solvent mixtures.The main study contents and innovative results are as follows:1)The solvent models were established through molecular dynamics method,and calculated the solubility parameters of different solvents,then,we compared and analyzed the miscibility of solvents.The radial distribution function(RDF)and the solvation free energy of CL-20 and HMX in various solvents were studied.The radial distribution function(RDF)and the solvation free energy of CL-20 and HMX in various solvents were studied.The results of them showed that it is feasible to mix the different solvents,and except for the miscibility of solvents,the interaction between solute and solvent should also be considered when selecting the components of the mixed solvents.2)The CL-20/HMX-solvent mixtures interface models were designed to investigate the effect of solvent mixtures on the formation and morphology of cocrystal explosives for the first time.Five kinds of solvent were selected as solvent mixtures components,namely 2-propanol,ethanol,methanol,acetone and dimethyl sulfoxide.The models were built according to the main growth surface of CL-20/HMX cocrystal.The binding energy,diffusion capacity of solvent molecules and modified attachment energy were analyzed from the differences of solvent behavior in solvent mixtures.The results show that the solvent mixtures of 2-propanol and dimethyl sulfoxide are harder to be adsorbed on cocrystal surfaces and the diffusion capacity of them are strong.The stability of CL-20/HMX composite in different solvent mixtures was studied by SMD model.The results show that cocrystal explosive molecules grow more freely and the stability of cocrystal molecules is the best in the presence of in 2-propanol and dimethyl sulfoxide mixed solvents.Cooperativity effect analysis showed that the solvent mixtures showed positive cooperativity effect,and the stability of CL-20/HMX composite was improved.The predicted cocrystal morphology by simulation in 2-propanol/dimethyl sulfoxide solvent mixture is consistent with the experimental result.3)Different molar ratios of solvent mixtures and CL-20/HMX cocrystal solvent interface models were dedigned.The behavior analysis of solvent molecules on the crystal surface showed that the the mainly interactions are between 2-propanol and cocrystal surface.The results of radial distribution function show that hydrogen bond interaction exists between hydrogen atom on CL-20/HMX cocrystal surfaces and oxygen atom of solvent molecules,and hydrogen bond and Van der Waals interaction exist simultaneously between oxygen atom of cocrystal and hydrogen atom of solvent molecules.The interaction between 2-propanol and cocrystal face is stronger than that between dimethyl sulfoxide and cocrystal face.The results of mass density distribution show that the solvent density on the cocrystal surface is larger when the ratio is 1:1,which indicates that the solvent molecules also have greater influence on the crystal surface morphology.The morphology of CL-20/HMX cocrystal calculated through MAE model is better when the ratio of 2-propanol: dimethyl sulfoxide is 1:1.The crystal morphology is blocky,and the aspect ratio is 2.15. |
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