Electronic structure and thermophysical properties of U3Si2: A systematic first principle study

Abstract Uranium silicides are considered to be prominent accident tolerant fuel for the light water reactors due to their high metal density and high thermal conductivity. Among the uranium silicon binary compounds, U 3 Si 2 is found to be advantageous. Here, we present a systematic first principles study of electronic structure and thermophysical properties of U 3 Si 2 within the framework of quasi-harmonic approximation. The relativistic effects have been treated through incorporating the spin-orbit interactions for all the calculations. The optimized cell volume from PBE method is found to be slightly underestimated, however, from the PBE+U method, it is found to be slightly overestimated as compared to the experimental volume, all the electronic structure results are comparable to the reported results. Volume dependant phonon frequencies have been calculated using the density functional perturbation theory to incorporate the effect of anharmonicity indirectly through quasi-harmonic approximation. Various thermophysical properties like free energy, thermal expansion, heat capacity, bulk modulus, etc. have been evaluated. The vibrational contribution alone to molar specific heat is found to be underestimated as compared to the experimentally reported results. Interestingly, incorporation of the electronic contribution is found to improve the results significantly. Electronic component of thermal conductivity has been calculated using the Boltzmann transport theory. The computed results are comparable to the available experimental results, which supports the reliability of the present study. All these predicted properties are very much important to gain knowledge about the U 3 Si 2 based fuel.