About this Abstract |
Meeting |
2020 TMS Annual Meeting & Exhibition
|
Symposium
|
Computational Materials Science and Engineering of Materials in Nuclear Reactors
|
Presentation Title |
DFT+U Point Defect Calculations of Uranium Mononitride |
Author(s) |
Bryant Jerome, Dilpuneet S. Aidhy |
On-Site Speaker (Planned) |
Dilpuneet S. Aidhy |
Abstract Scope |
DFT+U is used to capture the antiferromagnetic ground state of UN. However, the +U correction leads to possibilities of convergence to metastable states. We provide a comprehensive analysis of ground and metastable states and the resulting defect properties, from convergent supercells calculated using occupation matrix control (OMC), quasi-annealing (QA), and U-ramping. We preform each of these calculations using both the Dudarev and Liechtenstein rotationally-invariant forms of DFT+U. We find that QA and OMC are adequate to reach the ground state, whereas U-ramping tends to converge to metastable states. All three methods predict the N and U interstitials to be the most and least favorable defects respectively. The defect formation energies using the Dudarev form are 1.76 eV (U vacancy), 9.38 eV (U interstitial), 3.86 eV (N vacancy), and 0.94 eV (N interstitial). The results also show that there are significant deviations in defect formation energies across various metastable states. |
Proceedings Inclusion? |
Planned: Supplemental Proceedings volume |