Shock-induced transformations in crystalline RDX: A uniaxialconstant-stress Hugoniostat molecular dynamics simulation study

摘要

Molecular dynamics (MD) simulations of uniaxial shock compression along the [100] and [001]directions in the a polymorph of hexahydro-1,3,5-trinitro-1,3,5-triazine (α-RDX) have beenconducted over a wide range of shock pressures using the uniaxial constant stress Hugoniostatmethod [Ravelo et al., Phys. Rev. B 70, 014103 (2004)]. We demonstrate that the Hugoniostatmethod is suitable for studying shock compression in atomic-scale models of energetic materialswithout the necessity to consider the extremely large simulation cells required for an explicit shockwave simulation. Specifically, direct comparison of results obtained using the Hugoniostat approachto those reported by Thompson and co-workers [Phys. Rev. B 78, 014107 (2008)] based onlarge-scale MD simulations of shocks using the shock front absorbing boundary condition (SFABC)approach indicates that Hugoniostat simulations of systems containing several thousand moleculesreproduced the salient features observed in the SFABC simulations involving roughly aquarter-million molecules, namely, nucleation and growth of nanoscale shear bands for shockspropagating along the [100] direction and the polymorphic α- γ phase transition for shocks directedalong the [001] direction. The Hugoniostat simulations yielded predictions of the Hugoniot elasticlimit for the [100] shock direction consistent with SFABC simulation results.