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We use reverse non-equilibrium molecular dynamics (RNEMD) simulations todetermine the thermal conductivity in $\alpha$-RDX in the <100>, <010>, and<001> crystallographic directions. Simulations are carried out with theSmith-Bharadwaj non-reactive empirical interatomic potential [Smith &Bharadwaj, J. Phys. Chem. B 103, 3570(1999)], which represents thethermo-elastic properties of RDX with good accuracy. As an illustration, wereport the temperature and pressure dependence of lattice constants of$\alpha$-RDX, which compare well with experimental and ab initio results, as dolinear and volume thermal expansion coefficients, which we also calculate. Wefind that the thermal conductivity depends linearly on the inverse temperaturein the 200-400K regime due to the decrease in the phonon mean free path. Thethermal conductivity also exhibits anisotropy, with a maximum difference at300K of 24% between the <001> and <010> directions, an effect that remains whentemperature increases. Thermal conductivity in the <100> direction is mostlybetween the two other directions, although crossovers are predicted with <001>at high temperature, and <010> at low temperature under pressure. We observethat the thermal conductivity varies linearly with pressure up to 4 GPa. Thedata are fitted to analytical functions for interpolation/extrapolation and usein continuum simulations. MD results are validated against experiments usingimpulsive stimulated thermal scattering (ISTS) on RDX single crystals at 293Kand ambient pressure, showing good qualitative and quantitative agreement: sameordering between the three principal orientations, and an average error of 10%between the experiments and the model. These results provide confidence thatthe extracted analytical functions using the RNEMD methodology and theSmith-Bharadwaj potential can be applied to model the thermal conductivity of$\alpha$-RDX.

Pressure, temperature, and orientation dependent thermal conductivity of $\alpha$-1,3,5-trinitro-1,3,5-triazinane ($\alpha$-RDX)