First-principles study of oxygen adsorption and diffusion on the UN(001) surface

Nie, Jinlan; Ao, Lei; Zu, Xiaotao; Huang, He; Liu, K Z

doi:10.1088/0031-8949/90/12/125801

Cited by 3 publications

(4 citation statements)

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“…Whereas, in the case of M3 , where the O 2 molecule was aligned vertically on the Th atom, a bond formation with a bond length of 2.10 Å was observed between Th and O 2 , as shown in Figure ( M3 ). Comparing the results of O 2 adsorption at the (100) surface of ThN with that of uranium nitride (UN), we noticed for UN the O 2 prefers to be adsorbed in a dissociative mode as shown by a spontaneous dissociation of at all adsorption sites O 2 after structural optimization. In contrast, the spontaneous dissociative adsorption of O 2 occurred only at the M1 site on the ThN (100) surface.…”

Section: Resultsmentioning

confidence: 99%

“…The modeled surfaces contained repeated slabs of 48 ThN units arranged in 5 layers, thick enough to simulate the surface properties. 14 A vacuum of 15 Å was introduced to the surface models in the direction perpendicular to the surface, which is large enough to avoid interactions between periodic slabs. For the surface models, the BZ integration was done using a 2 × 2 × 1 Monkhorst-pack 18 k-point grid centered at gamma point.…”

Section: ■ Computational Detailsmentioning

confidence: 99%

“…From the fully optimized bulk structure, different surface structures corresponding to (100), (110), and (111) planes were created using the METADISE code, by considering the periodicity in the plane that results in a zero-dipole moment perpendicular to the surface plane. The modeled surfaces contained repeated slabs of 48 ThN units arranged in 5 layers, thick enough to simulate the surface properties . A vacuum of 15 Å was introduced to the surface models in the direction perpendicular to the surface, which is large enough to avoid interactions between periodic slabs.…”

Section: Computational Detailsmentioning

confidence: 99%

“…The difference in oxygen vacancy formation energies between UO 2 and PuO 2 is ascribed to the two actinides' redox properties. Nie et al 14 have studied the adsorption and diffusion of oxygen on the UN (100) surface and found that there is spontaneous dissociation of O 2 at all the adsorption sites considered. Hence, can we expect the O 2 to dissociate spontaneously on the ThN surface just like the UN?…”

Section: ■ Introductionmentioning

confidence: 99%

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Density Functional Theory Study of Oxygen Adsorption and Dissociation on Lower Miller Index Surfaces of ThN

et al. 2020

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Thorium nitride (ThN), a promising metallic nuclear fuel with higher actinide density and higher thermal conductivity, is investigated as a candidate nuclear fuel for the next generation of reactors. In this article, a systematic investigation of the adsorption mechanism of molecular (O2) and dissociated oxygen (O–O) for several configurations, on clean ThN (100), (110), and (111) surfaces, was performed using the density functional theory calculations. To elucidate the interfacial interaction of ThN with O2, an extensive examination of the relaxed adsorption structures, adsorption energies, electronic structure, changes in bond lengths, and the Bader charge transfer were conducted. The energetics and the most stable adsorption configurations of O2 at higher coverages are also reported. The results obtained indicate that the (100) surface is the most stable with a surface energy of 0.98 J/m2, followed by (111) and (110) with an energy of 1.68 J/m2 and 1.77 J/m2 respectively. The relaxed adsorption structures revealed that O2 has a stronger affinity for the thorium (Th) atom than the nitrogen (N) atom. The calculated interatomic bond distances of the Th–O bond was found to be consistent with the measured bond length of thorium oxide (ThO2), indicating the formation of the thorium oxide layer on the surface of ThN. Among all the different configurations considered on the (100) surface, only the O2 molecule placed at the Th–N bridge site has undergone spontaneous dissociation, whereas, in the case of (111) surface, the O2 molecule placed at the bridge site and the side-on Th site has undergone spontaneous dissociation. However, the O2 molecule adsorbed on the (110) surfaces of ThN requires activation energy for dissociation to occur. These observations in ThN surfaces are in stark contrast with the previously reported cases of uranium nitride (UN) and α-U (001), where all the configurations have undergone a spontaneous dissociation. Oxidation behavior of ThN is a critical issue that needs to be understood before researchers can push for its use in commercial reactors. In line with this thought, a molecular-level understanding of the surface chemistry of ThN in an oxygen environment is expected to provide information on the oxidation mechanisms.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Computational Detailsmentioning

confidence: 99%

Section: Computational Detailsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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