Theoretical Studies of the Reactions between Hyperthermal O(<sup>3</sup>P) and Graphite: Holes and the Second Layer
Bibliographic record
Abstract
Theoretical direct dynamic calculations on the basis of density functional theory are used to investigate hyperthermal collisions between O( 3 P) and highly oriented pyrolytic graphite (HOPG). The simulations suggest the HOPG surface becomes functionalized with epoxide groups as in previous works. Also, incoming O atoms can react at the surface to form O 2 by way of an Eley–Rideal mechanism when the surface exposed to colliding O atoms is already functionalized with epoxides. A second layer of pristine graphene, included in the model, absorbs collision energy and significantly reduces the rates of reactions that liberate carbon from the surface, compared to single-layer models. Semiquinone functional groups are thought to be common at graphitic sheet edges and holes and to be a major source of CO and CO 2 . We deploy a model to explore the behavior of semiquinones when exposed to hyperthermal oxygen atoms. These groups are found to lead to CO and to play a role in the formation of epoxide groups on the underlayer. Both of these findings are important in explaining the behavior of CO and O atoms observed in a recent set of experiments. Once produced, the CO remains associated with the sheet, interacting with the functional groups surrounding the hole for the remainder of the simulation. An epoxide group on the underlayer forms below the surface layer and would require the surmounting of two energy barriers to desorb, which is consistent with experimental predictions. CO 2 formation was also observed, and it resulted from an Eley–Rideal reaction as did the CO. Lactones form during some of the trajectories, and this functional group is thought to be important in the erosion of graphite caused by exposure to oxygen atoms. The exposure of lactones to hyperthermal O atoms is also explored, and it is found to lead predominantly to CO 2 .
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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 | 0.001 |
| 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 | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 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".