Calculations of the thermal conductivity of National Ignition Facility target materials at temperatures near 10 eV and densities near 10 g/cc using finite-temperature quantum molecular dynamics

Abstract

Using quantum finite-temperature density functional theory molecular dynamics (QMD), we performed simulations of several important materials in the Inertial Confinement Fusion-National Ignition Facility nominal target designs, comprising various mixtures of proposed ablator materials (Be or CH) with the DT fuel. Simulations were done over a range of temperatures between 5 eV and 20 eV, at densities between 7.5 and ∼12.5 g/cc. From the QMD trajectories, we calculated the electrical and thermal conductivity. We estimated the number of free electrons per atom by fitting the frequency-dependent electrical conductivity to the Drude formula. The thermal conductivity of the fuel increases with density but that of the ablator material is insensitive to modest density variations. We find that the thermal conductivity depends strongly on the ablator/fuel mix fraction but a Faber-Ziman interpolation scheme provides a reasonable approximation. We also compare our QMD results to the Hubbard and Lee-More models.