首页|First-principles investigation of uranium mononitride (UN): Effect of magnetic ordering, spin-orbit interactions and exchange correlation functional

First-principles investigation of uranium mononitride (UN): Effect of magnetic ordering, spin-orbit interactions and exchange correlation functional

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  • NSTL
  • Elsevier
Uranium mononitride (UN) is a promising nuclear fuel that combines the advantageous properties of readily used UO2 and uranium alloys. Various properties of UN have been previously studied using different density functional theory (DFT) methodologies; however, there are still inconsistencies when it comes to the dynamical stability and defect properties of UN. We address these inconsistencies by studying the UN phonons and defect properties using DFT calculations employing two generalized gradient approximation (GGA) exchange-correlation functionals: PBE and AM05, with and without an added on-site Coulomb repulsion term (+U). Furthermore, we investigate the importance of spin-orbit coupling (SOC) when calculating the properties of UN. We use the different methodologies to determine the preference of UN to have antiferromagnetic (AFM) ordering, as seen in experiments, or ferromagnetic (FM) ordering of the uranium spins. We compare the crystallographic properties, density of states, the DFT X-ray photoelectron spectra and phonon dispersions calculated using the different methodologies. We demonstrate that GGA + U reproduces the AFM ordering in UN, but the crystal structure is dynamically unstable. We also show that magnetic ordering is important in finding the lowest energy defective structure, and that SOC has a distinct influence on the energy of the different uranium interstitial defects. Lastly, we discuss the point defect formation energies under U-rich and N-rich conditions, and the stoichiometric formation energies calculated with the different methodologies, providing insight into the observed tendency for forming hypostoichiometric UN. (C)& nbsp;2021 Elsevier B.V. All rights reserved.& nbsp;

UNDFTDensity of statesMagnetic orderingCrystallographic propertiesPhononsPoint defectsStoichiometric reactionsINITIO MOLECULAR-DYNAMICSTOTAL-ENERGY CALCULATIONSAB-INITIOTHERMODYNAMIC PROPERTIESELECTRONIC-STRUCTUREPOINT-DEFECTS1ST-PRINCIPLESDFTSIMULATIONSTABILITY

Kocevski, Vancho、Rehn, Daniel A. A.、Andersson, David A. A.、Cooper, Michael W. D.

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Alamos Natl Lab

2022

10.1016/j.jnucmat.2021.153401

Journal of Nuclear Materials

Journal of Nuclear Materials

EISCI
ISSN：0022-3115
年,卷(期)：2022.559
  • 14
  • 51