Abstract
We present and discuss the results of the first-principles calculations of Frenkel defects and O impurities in uranium mononitride (UN) perspective for fast reactor nuclear fuels. Special attention is paid to the calculation of defect migration energies. We demonstrate that the interstitialcy mechanism (with the formation of a N-N dumbbell along the [1 1 1] axis) is energetically more favorable than the direct [1 0 0] hops. As a result, for the interstitial N ions we predict a diffusion mechanism similar to that known in isostructural fcc materials with a different chemical nature (KCl, MgO). The calculated effective N charge considerably depends on the ion position and environment (a host lattice site, interstitial or saddle point) which strongly limits the applicability of classical defect modelling based on formal invariant charges. Lastly, the calculated migration energy for the interstitial impurity O ions is quite low (2.84 eV), which indicates their high mobility and ability for reactions with other defects.
| Original language | English |
|---|---|
| Pages (from-to) | 2671-2675 |
| Number of pages | 5 |
| Journal | Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms |
| Volume | 266 |
| Issue number | 12-13 |
| DOIs | |
| Publication status | Published - 1 Jun 2008 |
| Externally published | Yes |
Funding
This study was partly supported by EC Framework 7 “F-Bridge” Project the Service Contract 204916-2006-04 F1ED KAR LV between ITU and ISSP, Riga, and the Latvian Council of Science (National Research Program on Energetics, Project No. 3). The authors are greatly indebted to Hj. Matzke, F. Wastin, R.A. Evarestov, E. Heifets, T. Wiss and M. Freyss for numerous discussions. The authors acknowledge the support from PNNL through proposal 25592 for making use of the computational resources of the EMSL.
Keywords
- Defect migration
- First-principles calculations
- Frenkel defects
- O impurity
- Supercell model
- Uranium mononitride (UN)
ASJC Scopus subject areas
- Nuclear and High Energy Physics
- Instrumentation
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