Multi-scale Dynamics Simulation Study On The Structure And Properties Of CL-20/TNT Cocrystal And Azide Polymers And Their Composites

In this paper,Molecular Dynamics（MD）and Dissipative Particle Dynamics（DPD）simulations are combined to investigate the properties of CL-20/TNT cocrystal,azide polymers and their composites.The details are as follows:（1）Reverse Nonequilibrium Molecular Dynamics（RNEMD）are applied to investigate the thermal conductivity of CL-20/TNT cocrystal.One-dimensional module of heat transportation are built,based on which,the thermal conductivity are derived via Fourier’s Law at steady state of conduction.The result of thermal conductivity at 1 atm and 298 K are 3.54 W·m^-1·K^-1.（2）Both specific volume and free energy simulation method are utilized to predict the melting point of CL-20/TNT cocrystal.For specific volume simulation method,MD simulations are carried out at different simulation times（1 ns,5 ns）and temperature intervals（25 K,15 K）.The simulation results of melting point at 1 atm are 449 K（1 ns,25 K）,447 K（5 ns,25 K）,429 K（1 ns,15 K）and 428K（5 ns,15 K）.All results are in reasonable agreement with the experimental value of 409 K under the perspective of MD research.Temperature intervals make stronger influence on the prediction of melting point than simulation times,comparing their results respectively.Therefore,temperature interval is major factor,while simulation time is minor factor in terms of prediction of the melting point by specific volume method.For free energy simulation method,simulations are taken at fixed simulation time of 1 ns and temperature gaps of 25 K and 15 K.Results of melting point at 1 atm are 426 K（1 ns,25 K）and 417 K（1 ns,15 K）,which are in better agreement than those of same simulation parameters in specific volume method with experimental result.Therefore,free energy simulations are a more efficient way predicting the melting point of CL-20/TNT cocrystal than specific volume method.（3）Dissipative Particle Dynamics are employed to study the compatibility of two PBX systems,（CL-20/TNT）/GAP and（CL-20/TNT）/Poly（AMMO/BAMO）,based on azide polymers.The analysis of the structure shows that Poly（AMMO/BAMO）is more compatible with CL-20/TNT cocrystal than GAP because it forms smaller and more evenly-distributed micelles in the CL-20/TNT matrix.