Ab initio molecular dynamics investigation of point defects in γ-U

Uranium (U) is often alloyed with molybdenum (Mo) or zirconium (Zr) in order to stabilize the high-temperature body-centered cubic γ phase of uranium for use in nuclear reactors. However, relatively little experimental or computational investigation has centered on γ-U, largely due to the mechanical instability of this phase at room temperature. This is particularly problematic for density functional theory calculations that typically investigate 0 K properties. However, ab initio molecular dynamics (AIMD) allows for quantum mechanical-based calculations to be performed at non-zero temperatures. In this work, AIMD simulations are performed to calculate the equilibrium volume for the γ phase of U from 900 K to 1400 K. Utilizing the volume at each temperature, the bulk modulus, the radial distribution function, the interstitial and vacancy formation energies, and the diffusion coefficients are determined.