Molecular Dynamics Calculations On The Phase Transitions And Chemical Reactions Of CL-20 Explosives

Explosive phase transitions and reactions processes are very complicated. In the the atom and molecule scales, calculation the phase transitions and reactions processes of explosive, can understand the nature of phase transitions and reactions processes. It is very important to research the explosive detonation mechanisms and the safety of explosive. In this paper, molecular dynamics simulations were employed to study the mechanisms of phase transitions and chemical reactions of CL-20 explosives.Based COMPASS force field, the isothermal-isobaric molecular dynamics simulations methods were employed to study the crystal lattice parameters of different polymorphs of CL-20 supercells. The relationships between the lattice parametersat different temperatures indicate that the COMPASS force field would describe thedifferent polymorphs of CL-20 supercells. By analyzing the lattice parameters under different temperatures and densities under different temperatures, the phase transitions of different CL-20 supercells were calculated. When the target temperature reaches 360 K, ? phase CL-20 supercells occurs phase transition; when the temperature reaches 450 K, ?phase CL-20 and ? phase CL-20 supercells occurs phase transition; when the temperature reaches 490 K,? phase CL-20 supercell occurs phase transition.By using Reax FF force field molecular dynamics simulations, based on canonical ensemble, isothermal-isobaricensemble and Berendsen thermostat and Berendsen barostat, the thermal decomposition processes of signal ? phase CL-20 molecule betweent 1000 K to 2500 K temperature regime were studied. The results of calculation indicatedthat the initial decomposition pathway of ? phase CL-20 molecule is only the N-N dissociation in CL-20 molecule, leading nitro functional groups separate from five-membered rings and six-membered ring of the host molecules, to form NO2 molecules.Based on periodic boundary conditions, the different supercell calculation modelsfor Reax FF molecular dynamics simulations of ?phase CL-20, ?phase CL-20, ?phase CL-20 modifications were built. By using Reax FF force field,canonical ensemble, isothermal-isobaricensemble, Berendsen thermostat which controls the different calculation models temperature and Berendsen barostat which controls the different calculations models pressure, the thermal decomposition processes of ?phase, ?phase, ?phasemodifications at various temperatures were studied betweent 1000 K to 3000 K temperature regimes. By analyzing the effects the molecular packing methods, temperature on the thermal decomposition process of CL-20 supercells, the initial decomposition mechanisms of different modifications CL-20 supercellswere determined.The different supercell calculation modelsfor the impacting reactive molecular dynamics simulations of CL-20 were built. By using Reax FF-lgforce field, based on isothermal-isobaricensemble and microcanonical ensemble, the decomposition of? phase CL-20 and ?hydrate phase CL–20 supercells under impact conditions were calculation. By analyzing the types and numbers of products in two supercells under under different impact conditions, the main reactive chemical types of ? phase CL-20 molecules in two ? phase CL-20 supercells were given.