Trapping Properties of Iodine, Cesium, and Tellurium in Uranium Dioxide: A DFT+ Study.

We investigate the trapping properties of iodine, cesium, and tellurium in uranium dioxide, using the Hubbard-corrected density functional theory (DFT+). In order to avoid the metastable states inherent to this method, we use the occupation matrix control (OMC) scheme, which also allows us to monitor the oxidation states of the different species. The most favorable trapping sites, oxidation states, and solubility of I, Cs, and Te are evaluated in stoichiometric UO.

Structural, electronic and energetic properties of uranium-americium mixed oxides [Formula: see text] using DFT[Formula: see text] calculations.

In this paper, we determine for the first time the electronic, structural and energetic properties of [Formula: see text] mixed oxides in the entire range of Am content using the generalized gradient approximation (GGA)[Formula: see text] in combination with the special quasirandom structure (SQS) approach to reproduce chemical disorder. This study reveals that in [Formula: see text] oxides, Am cations act as electron acceptors, whereas U cations act as electron donors showing a fundamental difference with [Formula: see text] or [Formula: see text] in which there is no cation valence change in stoichiometric conditions compared to the pure oxides. We show for the first time that the lattice parameter of stoichiometric [Formula: see text] follows a linear evolution which is the structural signature of an ideal solid solution behavior.

Electronic Structure Investigation of the Bulk Properties of Uranium-Plutonium Mixed Oxides (U, Pu)O.

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.

Determination of Krypton Diffusion Coefficients in Uranium Dioxide Using Atomic Scale Calculations.

We present a study of the diffusion of krypton in UO using atomic scale calculations combined with diffusion models adapted to the system studied. The migration barriers of the elementary mechanisms for interstitial or vacancy assisted migration are calculated in the DFT+U framework using the nudged elastic band method. The attempt frequencies are obtained from the phonon modes of the defect at the initial and saddle points using empirical potential methods.

DFT + U investigation of charged point defects and clusters in UO2.

We present a physically justified formalism for the calculation of point defects and cluster formation energies in UO2. The accessible ranges of chemical potentials of the two components U and O are calculated using the U-O experimental phase diagram and a constraint on the formation energies of vacancies. We then apply this formalism to the DFT + U investigation of the point defects and cluster defects in this material (including charged ones).