Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session P11: Dopants and Defects in Semiconductors - Oxides
2:30 PM–5:30 PM,
Wednesday, March 7, 2018
LACC Room: 303A
Sponsoring Units: DMP DCOMP FIAP
Chair: Joel Varley, Lawrence Livermore National Laboratory
Abstract: P11.00009 : Ab initio calculation of lattice constant variations with stoichiometry: Application to UO2+x
4:30 PM–4:42 PM
Non stoichiometric uranium dioxide experiences a shrinkage of its lattice constant with increasing oxygen content, for both the hypo- and the hyper-stoichiometric regimes. Based on ab initio calculations within the DFT+U approximation, we have developed a point defect model that accounts for the volume of relaxation of the most significant intrinsic defects of UO2. Our model takes a special care about the treatment of the charged defects in the equilibration  and in the determination of reliable defect volumes of formation .
In the hypostoichiometric regime, the charged oxygen vacancies are dominant and explain the lattice constant variation
with their unexpected positive volume of relaxation.
In the hyperstoichiometric regime, the uranium vacancies are predicted to be the dominating defect in contradiction with experimental observations. However, disregarding uranium vacancies allows us to recover a good match for the lattice constant variation as a function of stoichiometry. This can be considered as a new clue that the stability of uranium vacancies within DFT+U is indeed spurious.
 J.P. Crocombette, D. Torumba, and A. Chartier, Phys. Rev. B 83, 184107 (2011).
 F. Bruneval, C. Varvenne, J.P. Crocombette, E. Clouet, Phys. Rev. B 91, 024107 (2015).
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