Density Functional Theory Study of Oxygen Adsorption and Dissociation on Lower Miller Index Surfaces of ThN
Bibliographic record
Abstract
Abstract 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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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".