Molecular Dynamics Simulations On The Reaction Mechanism Of HNS Under High Temperature And High Pressure

2,2′,4,4′,6,6′-Hexanitrostilbene(HNS)is a typical heat-resistant explosive with excellent thermal stability and sensitivity to short shock pulses.It is widely used in in-line explosive trains and oil exploitation fields.Therefore,the thermal decomposition mechanism of HNS has attracted a great deal of interest.We use molecular dynamics simulations with developed ReaxFF reactive force fields to examine the reaction mechanism of HNS under high temperature,high pressure and impact.Using LAMMPS software package,we constract a 2×4×2 HNS supercell.The decomposition mechanism of HNS is investigated at various temperatures by ReaxFF-lg reactive force field using NVE ensemble.The temperature is controlled by Berendsen method.The results show that the main initial decomposition mechanism of HNS are C-NO2 bond dissociation and nitro-nitrite(NO2-ONO)isomerization.The main products of HNS thermal decomposition are H2 O,CO2,N2,H2,HONO,and HNO.The final products are H2 O,CO2,N2,and H2.The cluster size is larger at lower temperature.In addition,further reactions are delayed because of the deficiency of O in the clusters.In order to study the reactive mechanism of thermal decomposition of HNS under high pressure,the system is condensed using NPT ensemble.The thermal decomposition of HNS under different pressure at 3500 K is studied.The results show that pressure significantly hinders the initial decomposition process of HNS.The size of clusters increases when the pressure increases.A great deal of O atoms are confined to the clusters,hindering the further reaction.ReaxFF molecular dynamics simulation combining with MSST technique is used to study the shock initial mechanism of HNS.The shock wave at various velocities are loaded by axial compression.We analyse the thermodynamic properties during impact compression process,the relationship between impact velocity and particle velocity,the main chemical reactions,the evolution of products and clusters.Higher impact velocity will accelerate the reaction,but the reaction degree becomes lower.Impact significantly inhibited the abstraction of O atoms from the clusters.Further reactions are delayed because of the deficiency of O in the clusters.