Electronic Structure Investigation of the Bulk Properties of Uranium–Plutonium Mixed Oxides (U, Pu)O₂

Abstract

We present electronic structure calculations of bulk properties of (U, Pu)O, in the whole Pu content range for which only very few experimental data are available. We use DFT+U and the vdW-DF functional in order to take into account the strong 5f electron correlations and nonlocal correlations. We investigate structural, elastic, electronic, and energetic properties of (U, Pu)O in the approximation of the ideal solid solution as described by the special quasirandom structures (SQS) method. The results on electronic properties highlight the narrowing of the band gap due to the mixing of UO and PuO. Results on the mixing enthalpy are used to describe the phase stability of (U, Pu)O solid solutions, using both SQS configurations and a parametric method. In particular, the issue of an ideal solid solution on a limited supercell size is discussed.

First-principles investigation of the bulk properties of americium dioxide and sesquioxides

“…Method evolution of the U value does not have a significant influence on the band gap. Concerning the bulk modulus, our calculated values, 135 GPa for C-type and 139 GPa for B-type, follow the same trend as the ones obtained in Pu 2 O 3 (137-164 GPa) using DFT+U [17]. Concerning the A-type structure the bulk modulus remains the same when U varies.…”

“…Whereas the onsite Coulomb interaction U and exchange J are well known for UO 2 [11,12], this is not the case for americium oxides, for which literature does not agree on any value since these values strongly vary from one author to another [7,[13][14][15]. Actinide oxides have been extensively studied by the DFT+U [12,[16][17][18] method. Thus, we use the DFT+U method in this paper and we purpose to provide the optimal values of the U and J parameters for americium oxides, which will be used in a subsequent study to evaluate the effect of americium in mixed actinide oxides.…”

Electronic and magnetic properties of yttria-stabilized zirconia (6.7 mol% in Y2O3) doped with Er3+ ions from first-principle computations

“…Being aware of the well-known deficiencies of conventional pure DFT [59] in describing strongly correlated systems, we chose the hybrid PBE0, HSE06 and the pure PBE functionals, respectively. In the latter approximation, the Hubbard correction term has been also employed [60][61][62][63][64]. In all cases, we applied the spin-polarized generalized gradient approximation (SGGA ?…”

“…In a further step, we calculated the magnetic anisotropy energy (MAE) of YSZ 6.7 mol% in Er 2 O 3 defined as the difference between the total energies of a magnetic material for different orientations of the magnetization. For that purpose, we used the SGGA method including spin-orbit coupling (SOC) [62] taking also into account the Hubbard term (U) [63].…”

Structural, electronic and energetic properties of uranium–americium mixed oxides ${\rm U}_{1-y}{\rm Am}_y{\rm O}_2$ using DFT$+{U}$ calculations

“…To evaluate the stability of alloyed compounds, the free enthalpy of mixing is usually considered [4,5,32]. The Gibbs free energy of mixing refers to the energy difference of a configurationally random alloy where the atomic species randomly occupy lattice positions [33] with respect to the pure compounds.…”