First-principles investigations on the interface structure, stability and electronic properties of UN/ZrC for dispersion nuclear fuel

Based on first-principles density functional theory calculations, we investigate the structure, stability and electronic properties of UN/ZrC interface in the context of UN fuel particles dispersed in ZrC matrix, aiming to understand the effects of particle size and interfacial defects on the stability of the dispersion nuclear fuel elements. We first compare different contact configurations of UN/ZrC with (100), (110) and (111) orientations, and identify the most stable structures with the lowest total energy. The calculated binding energies between UN and ZrC in these interfaces are 3.2∼8.5 J/m², indicative of high stability. By using UN/ZrC(100) interface as a prototype probe, we explore UN films of one to nine atomic layers, which reveal that the binding strength oscillates only below three layers and converges quickly with higher thickness. This can be explained by orbital hybridization and charge redistribution that leads to reduced quantum size effect of thin films. We further demonstrate that interfacial defects, including various vacancies and exchanged atoms, generally reduce the binding strength. These results not only shed light on the understanding of UN/ZrC interface at an atomic scale, but also provide valuable guidance for future fabrication and implementation of novel nuclear fuels for practical applications.