Lattice changes versus initial numbers of oxygen Frenkel pairs in MD supercells.

<p>The values given near the data points represent the numbers of obstruction type oxygen FPs in the MD supercell at the ends of simulations. The inset is taken from Ref. 17 and shows experimental data for lattice parameter changes that result from defect ingrowth as a function of increasing fission dose.</p

Number of uranium FPs versus IFPs, calculated using the Yakub and Günay potentials.

<p>Number of uranium FPs versus IFPs, calculated using the Yakub and Günay potentials.</p

Equilibrium state from the <110> direction of a UO₂ supercell with 17 uranium IFPs seen.

<p>Distortion and obstruction type uranium (gray) defects are indicated with arrows. Distortion type defects are ions that have been slightly displaced into channels. Obstruction type defects are ions that occupy central positions within channels; they occupy special positions, have a constant coordination number, and can be considered to be ions trapped in cages. There is a relationship between the ingrowth of obstruction type defects and radiation-induced lattice expansion.</p

Relative lattice expansions of different types of defects: circles indicate oxygen, triangles uranium.

<p>(a) Oxygen distortions (b) uranium obstructions (c) oxygen obstructions + distortions and (d) uranium obstructions + distortions.</p

Radial distribution function, <i>g</i>_<i>uu</i>(<i>r</i>), of a 5×5×5 MD UO₂ supercell with 17 uranium IFPs.

<p>Obstruction and distortion type defects are indicated on the graph. Obstruction type defects have sharper boundaries (pre-peaks) than distortion type defects.</p

Initial view from the x direction of a MD supercell sample with 20 oxygen IFPs.

<p>Arrows indicate the displacements of atoms from their lattice sites to their interstitial positions. Each color represents a different layer along the x direction.</p

Relative lattice expansion versus number of obstruction type uranium defects, from Yakub and Günay potentials.

<p>Relative lattice expansion versus number of obstruction type uranium defects, from Yakub and Günay potentials.</p

Relative lattice expansions.

<p>(a) Total number of defects after equilibration and (b) initial number of uranium FPs. The inset was taken from Ref. 21 and presents experimental lattice expansion data as a function of cumulative dose.</p

Relative lattice expansion versus number of uranium IFPs, calculated using the Yakub and Günay potentials.

<p>The inset was taken from Ref. 21 and shows experimental lattice expansion as a function of cumulative dose.</p