Ab initio DFT+U Study of He Atom Incorporation into UO2 Crystals

Journal Article · Thu May 28 04:00:00 UTC 2009 · Physical Chemistry Chemical Physics. PCCP, 11(33):7241-7247

DOI:https://doi.org/10.1039/b907233k· OSTI ID:1001523

Gryaznov, D; Heifets, Eugene; Kotomin, E A

We present and discuss results of the 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 anti-ferromagnetic UO2 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 UO2. We discuss also the problem of a conducting electronic state arising when He is placed into a tetragonal antiferromagnetic 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 ab initio DFT calculations.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1001523
• Journal Information: Physical Chemistry Chemical Physics. PCCP, 11(33):7241-7247, Journal Name: Physical Chemistry Chemical Physics. PCCP, 11(33):7241-7247 Journal Issue: 33 Vol. 11; ISSN 1463-9076
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
APPROXIMATIONS
ATOMS
DEFECTS
Environmental Molecular Sciences Laboratory
FUNCTIONALS
HUBBARD MODEL
INTERSTITIALS
JAHN-TELLER EFFECT
MONOCLINIC LATTICES
POLARIZATION
SHELL MODELS
SIMULATION
SPIN
SYMMETRY