First Principles Simulations on Surface Properties and Oxidation of Nitride Nuclear Fuels

Zhukovskii, Yuri F.; Bocharov, Dmitry; Gryaznov, Denis; Kotomin, Eugene A.

doi:10.5772/34144

Cited by 6 publications

(3 citation statements)

References 54 publications

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“…This observation follows with Tasker’s analysis, in which the (100) surface must have the lowest surface energy for the rock-salt structure. However, there is the possibility of forming other crystallographic orientations in nanoparticles and polycrystalline materials . In addition, temperature gradients also play an essential role during crystal growth, as observed in other rock-salt structures such as NaCl. , Therefore, besides understanding the oxidation mechanism of the dominating (100) surface, it is also essential to investigate oxides’ formation on other lower Miller indices in ThN.…”

Section: Resultsmentioning

confidence: 99%

“…However, there is the possibility of forming other crystallographic orientations in nanoparticles and polycrystalline materials. 46 In addition, temperature gradients also play an essential role during crystal growth, as observed in other rock-salt structures such as NaCl. 47,48 Therefore, besides understanding the oxidation mechanism of the dominating (100) surface, it is also essential to investigate 6 and 7.…”

Section: ■ Computational Detailsmentioning

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%

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

et al. 2020

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“…However, as real surfaces are never perfect but contain defects due to the method of synthesis or service conditions, in the present work, we have explored the effects of U and Si vacancies on the adsorption mechanisms of water and oxygen on the {001}, {110}, and {111} surfaces of U 3 Si 2 . Surface vacancies in UN, UO 2 , PuO 2 , and CeO 2 have been shown in previous studies to affect the oxidation behavior of such surfaces in the presence of oxidizing and hydriding agents. ,,− The fundamental aspects of oxygen and water adsorption, including the initial adsorption geometries, adsorption energies, structural parameters, and electronic properties, are presented. Our results reveal a chemical picture of the initial steps involved in the oxidation process of the U 3 Si 2 surfaces in the presence of oxygen and water (considering both molecular and dissociative adsorption).…”

Section: Introductionmentioning

confidence: 96%

DFT +UStudy of the Adsorption and Dissociation of Water on Clean, Defective, and Oxygen-Covered U₃Si₂{001}, {110}, and {111} Surfaces

et al. 2019

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The interfacial interaction of U 3 Si 2 with water leads to corrosion of nuclear fuels, which affects various processes in the nuclear fuel cycle. However, the mechanism and molecular-level insights into the early oxidation process of U 3 Si 2 surfaces in the presence of water and oxygen are not fully understood. In this work, we present Hubbard-corrected density functional theory (DFT + U) calculations of the adsorption behavior of water on the low Miller indices of the pristine and defective surfaces as well as water dissociation and accompanied H 2 formation mechanisms. The adsorption strength decreases in the order U 3 Si 2 {001} > U 3 Si 2 {110} > U 3 Si 2 {111} for both molecular and dissociative H 2 O adsorption. Consistent with the superior reactivity, dissociative water adsorption is most stable. We also explored the adsorption of H 2 O on the oxygen-covered U 3 Si 2 surface and showed that the preadsorbed oxygen could activate the OH bond and speed up the dissociation of H 2 O. Generally, we found that during adsorption on the oxygen-covered, defective surface, multiple water molecules are thermodynamically more stable on the surface than the water monomer on the pristine surface. Mixed molecular and dissociative water adsorption modes are also noted to be stable on the {111} surface, whereas fully dissociative water adsorption is most stable on the {110} and {001} surfaces.

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LCAO Calculations on Uranium Nitrides

Ėvarestov

2012

Springer Series in Solid-State Sciences

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First Principles Simulations on Surface Properties and Oxidation of Nitride Nuclear Fuels

Cited by 6 publications

References 54 publications

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

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

DFT +UStudy of the Adsorption and Dissociation of Water on Clean, Defective, and Oxygen-Covered U₃Si₂{001}, {110}, and {111} Surfaces

LCAO Calculations on Uranium Nitrides

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First Principles Simulations on Surface Properties and Oxidation of Nitride Nuclear Fuels

Cited by 6 publications

References 54 publications

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

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

DFT +UStudy of the Adsorption and Dissociation of Water on Clean, Defective, and Oxygen-Covered U3Si2{001}, {110}, and {111} Surfaces

LCAO Calculations on Uranium Nitrides

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Product

Resources

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DFT +UStudy of the Adsorption and Dissociation of Water on Clean, Defective, and Oxygen-Covered U₃Si₂{001}, {110}, and {111} Surfaces