Developing an ab initio Quality Pairwise Potential for Large Scale Molecular Dynamics Simulations of Deuterium under Inertial Confinement Fusion Conditions*

Simulations of inertial confinement fusion (ICF) experiments commonly use radiation-hydrodynamic codes, which are insufficient for modeling kinetic processes such as species separation in CH plastic ablators and the subsequent hydrogen streaming and mixing into the deuterium-tritium (DT) fuel. This requires atomistic level microscopic physics that is beyond the scope of single fluid hydrodynamic models but can be naturally accounted for by classical molecular dynamics (CMD).

However, the requirement of interatomic potentials that remain accurate from ambient to extreme densities (ρ) and temperatures (T) as found in an ICF experiment also poses challenges to CMD. In this work, we use the iterative Boltzmann inversion (IBI) technique to develop a ρ, T, and radial dependent pairwise potential for deuterium that accurately reproduces the radial distribution functions and pressure-ρ relations along the Hugoniot from ab initio MD simulations, for ρ between 0.1-1.0 g/cc and T between 1,000–250,000 K.

Further work is in progress toward automating the use of the IBI potentials in non-equilibrium shock simulations, and if successful, generation of potentials for CH-DT compounds for simulations of the ablator-fuel interface with ab initio levels of accuracy.