Theoretical study of the gaseous hydrolysis of NO2 in the presence of NH3 as a source of atmospheric HONO
Bibliographic record
Abstract
Environmental context Nitrous acid is an important atmospheric trace gas, but the sources and the chemical mechanisms of its production are not well understood. This study explores the effects of ammonia and water on the hydrolysis of nitrogen dioxide and nitrous acid production. The calculated results show that ammonia is more effective than water in promoting the hydrolysis reaction of nitrogen dioxide. Abstract The effects of ammonia and water molecules on the hydrolysis of nitrogen dioxide as well as product accumulation are investigated by theoretical calculations of three series of the molecular clusters 2NO2–mH2O (m = 1–3), 2NO2–mH2O–NH3 (m = 1, 2) and 2NO2–mH2O–2NH3 (m = 1, 2). The gas-phase reaction 2NO2 + H2O ? HONO + HNO3 is thermodynamically unfavourable. The additional water or ammonia in the clusters can not only stabilise the products by forming stable complexes, but also reduce the energy barrier for the reaction. There is a considerable energy barrier for the reaction at the reactant cluster 2NO2–H2O: 11.7 kcal mol–1 (1 kcal mol–1 = 4.18 kJ mol–1). With ammonia and an additional water in the cluster, 2NO2–H2O–NH3, the thermodynamically stable products t-HONO + NH4NO3–H2O can be formed without an energy barrier. With two ammonia molecules, as in the cluster 2NO2–mH2O–2NH3 (m = 1, 2), the reaction is barrierless and the product complex NH4NO2–NH4NO3 is further stabilised. The present study, including natural bond orbital analysis on a series of species, shows that ammonia is more effective than water in promoting the hydrolysis reaction of NO2. The product cluster NH4NO2–NH4NO3 resembles an alternating layered structure containing the ion units NH4+NO2– and NH4+NO3–. The decomposition processes of NH4NO2–NH4NO3 and its monohydrate are all spontaneous and endothermic.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.006 | 0.001 |
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".