First-principles study of surface properties of uranium silicides

Abstract Uranium silicides are currently under investigation as accident tolerant fuels for light water reactors because of its high uranium density and high thermal conductivity. Surface energy as an important material property is required for modeling of gas bubble behavior in nuclear fuels using mesoscale approaches, such as phase field and rate theory methods. However, there is no such information available for uranium silicides from either experiment or theory. To this end, we study the surface properties of two uranium silicide compounds U3Si2 and U3Si using first-principles calculations. Of the low-index facets of tetragonal U3Si2 and U3Si, we study a total of 13 surfaces up to a maximum Miller index of 3. From the calculated surface energies, the equilibrium single crystal shapes of U3Si2 and U3Si are obtained using Wulff construction. The dominant surface orientation, surface area weighted surface energy and surface anisotropy are predicted. The obtained surface properties of U3Si2 and U3Si can be used for an accurate description of the morphology of fission gas bubbles in uranium silicide fuels in the future.