Title: Ab initio DFT+U Study of He Atom Incorporation into UO2 Crystals
Citation: PHYSICAL CHEMISTRY CHEMICAL PHYSICS vol. 11 p. 7241-7247
Publication Year: 2009
JRC N°: JRC56743
ISSN: 1463-9076
DOI: 10.1039/b907233k
Type: Articles in periodicals and books
Abstract: Wc present and discuss results of lhe density functional theory (DFT) for perfect UO2 crystals with He atoms in octahedral interstitial positions therein. We have calculated basic bulk crystal properties and He incorporation energies into the low temperature ami-ferromagnetic UCh phase using several exchange-correlation functionals within the spin-polarized local density (LDA) and generalized gradient (GGA) approximations. In all DFT calculations we included the on-site correlation corrections using the Hubbard model (DFT+ U approach). We analysed a potential crystalline symmetry reduction from tetragonal down to orthorhombic structure and confirmed the presence of the Jahn-Teller effect in a perfect UO?. We discuss also the problem of a conducting electronic state arising when He is placed into a tetragonal an ti ferromagnetic phase of UO2 commonly used in defect modelling. Consequently, we found a specific monoclinic lattice distortion which allowed us to restore the semiconducting state and properly estimate He incorporation energies. Unlike the bulk properties, the He incorporation energy strongly depends on several factors, including the supercell size, the use of spin polarization, the exchange-correlation functionals and on-site correlation corrections. We compare our results for the He incorporation with the previous shell model and ah initio DFT calculations,
JRC Directorate:Nuclear Safety and Security

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