Self-irradiation Damage in α-Uranium: an Ab Initio Study

The α phase is a stable isotope of uranium at low temperatures (below 934 K) and has highly asymmetric face-centered orthorhombic structure. Understanding the radiation damage in α-uranium (α-U) is of central importance to modeling the behavior of uranium-based fuels. Threshold displacement energy (TDE) is regarded as one of the fundamental quantities to study the radiation damage in materials. The TDE is used in radiation damage theory within Kinchin-Pease models or NRT equations to estimate the number of displacements per atom over the extended time. It is therefore critical to determine the accurate values of the TDE to quantify the radiation damage. The classical molecular dynamics based on empirical potentials are unable to reliably capture the interatomic forces and fail to model lattice defects and recovery. So, in this work, we use ab initio molecular dynamics (AIMD) to perform primary-knock-on-atom (PKA) simulations in α-U along different crystallographic directions. We then determine the accurate values for the TDE along the studied directions and calculate the average TDE. We also study the evolution of the local structure in α-U for varying PKA energies.