Structural, electronic, elastic and thermal properties of Cr-doped U3Si2: A DFT study

Alloying has been considered as an effective strategy to make up for the poor oxidation corrosion resistance of U ₃Si ₂. However, the theoretical studies on alloyed U ₃Si ₂ are rarely reported. In this study, the structural, electronic, elastic and thermal properties of 10at% Cr-doped U ₃Si ₂ were studied using first principles calculations and semiclassical Boltzmann transport theory. Our results show that the U ₃Si _1.5Cr _0.5 phase is determined to be thermodynamically, dynamically and elastically stable, and U _2.5Si ₂Cr _0.5 phase is dynamically and elastically stable. U ₃Si _1.5Cr _0.5 is more stable than U _2.5Si ₂Cr _0.5 from the thermodynamic calculation results. From the calculated electronic structure results, a mixture of ionic and metallic bonds dominates the bonding of Cr-doped U ₃Si ₂ . They are ductile materials compared to the brittleness of U ₃Si ₂ according to the results of B/ G ratio, Cauchy pressure and Poisson`s ratio. Moreover, U ₃Si _1.5Cr _0.5 is a nearly elastic isotropic material, while U _2.5Si ₂Cr _0.5 exhibits strong anisotropy. The thermal conductivity of Cr-alloyed U ₃Si ₂ is dominated by the electronic contribution at high temperature, which is lower than U ₃Si ₂ but higher than UO ₂ at service temperature and increases with temperature. Therefore, in addition to significantly improving the resistance to oxidation and corrosion of U ₃Si ₂ , Cr doping can also convert the brittleness of U ₃Si ₂ into toughness and improve its machinability, albeit at the reasonable expense of some mechanical properties and thermal conductivities, while maintaining the high uranium density of U ₃Si ₂ fuel form. The results of this work may provide useful clues for the application and improvement of uranium silicide fuels.