Transport Properties\nof Liquid Pentaerythritol Tetranitrate\n(PETN) from Molecular Dynamics Simulations

We have used molecular dynamics simulations to determine\nthe transport\nproperties of liquid pentaerythritol tetranitrate (PETN), an important\nenergetic material. The density, ρ, self–diffusion coefficient, <i>D</i>, thermal conductivity, κ, and shear viscosity, μ,\nhave been computed over pressures and temperatures relevant to the\nsubshock regime (up to 1000 K and a few GPa), where PETN is known\nto melt prior to initiation. We find that the thermal conductivity\nκ(<i>P</i>, <i>T</i>) can be represented\nby a simple analytical function that fits the data points with very\ngood accuracy, even beyond the subshock regime, up to 2000 K and 20\nGPa. The self–diffusion coefficient, <i>D</i>, exhibits\nnonmonotonic behavior, with notably the temperature-independent prefactor\ndecreasing by several orders of magnitude between 0 and 2 GPa before\nremaining nearly constant after, and the activation energy varying\nlittle in the subshock regime before increasing linearly beyond. Lastly,\nthe viscosity, μ, is well described by Nahme’s law, which\nis fitted to the MD results and allows us to predict μ(<i>P</i>, <i>T</i>) for temperatures and pressures corresponding\nto the subshock regime. These results can be used to model the response\nof PETN to low-velocity impacts, where the material melts prior to\nthe first reactions, and thermal conduction and viscosity play a crucial\nrole.