First-principles investigations on the anisotropic elasticity and thermodynamic properties of U3Si2–Al

U3Si2 has been tested as a new type of nuclear fuel, and Al has been proven to improve its oxidation resistance. However, there is no research on its anisotropic mechanical and thermal properties. The mechanical and thermal properties of Al-alloyed U3Si2 nuclear fuel are calculated on the basis of first principles. Through the phonon dispersion curves, two kinetic stable structures sub-U3Si1.5Al0.5 and sub-U2.5Si2Al0.5(I) are screened out. It is found that the toughness of these two compounds after alloying are significantly improved compared to U3Si2. The three-dimensional Young's modulus shows that, the sub-U3Si1.5Al0.5 formed by Al alloying in U3Si2 maintains a higher mechanical isotropy, while sub-U2.5Si2Al0.5(I) shows higher mechanical anisotropy, which is consistent with the value of Au. The calculation result shows that the lattice thermal conductivity of sub-U3Si1.5Al0.5 and sub-U2.5Si2Al0.5(I) after alloying exhibits high isotropy as the temperature increases.