Molecular dynamics simulations of deuterium-boron interactions at fusion-relevant energies

Boronization is a commonly used method of plasma-facing material conditioning. The application of the boron results in an increase in plasma performance due to impurity species (namely, oxygen) being chemically trapped on the surface of the boron. The reactive nature of these boron films also raises questions around hydrogen retention and diffusion. In this work, ion bombardment of boron films was simulated using the molecular dynamics code Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) with reactive force field (ReaxFF) potentials. The deuterium ions were simulated at fusion-relevant energies (25 – 200 eV) at various incident angles (0° – 85°) for 1000 ions, equivalent to a fluence of ~4 x 10¹⁹ D m^-2. Deuterium retention probabilities, particle reflection energy and angle distribution, and boron sputtering yields were measured and analyzed. These results were then compared to binary collision approximation (BCA) calculations, which are commonly used to model the surface response in Monte Carlo impurity transport models. While BCA methods are accurate for higher energy ions, at energies <50 eV the measured quantities are starkly different between the two models.