Pressure and temperature dependent thermal conductivity tensor of high explosive crystals

Modeling and simulation are critical for predicting the performance and safety of high explosives (HE), in particular their response to moderate insults in accident scenarios.  Thermal conductivity, notably, is a key component of HE modeling: heat localization leads to the creation of “hot spots” where chemical reactions occur, ultimately causing events such as deflagration of detonation; heat conduction limits the temperatures accessible in hot spots and thus has a major impact on these phenomena. However, experimental information on thermal conductivity is usually scarce, and rarely accounts for temperature, pressure, and orientation dependence, which are critical input to higher-scale simulations. In this work, we use reverse non-equilibrium molecular dynamics (RNEMD) to determine the thermal conductivity of three important HEs: orthorhombic α-1,3,5-trinitro-1,3,5-triazinane (α-RDX), monoclinic β-1,3,5,7-tetranitro-1,3,5,7-tetrazoctane (β-HMX), and tetragonal pentaerythritol tetranitrate (PETN). Importantly, we compute the full thermal conductivity tensor for these compounds, as a function of temperature and pressure, allowing for the determination of heat transport in any direction, and for thermodynamic conditions that span the stability range of the material. The results compare well with available experimental data.