Characterization of sputtering products during graphite exposure to deuterium ions by molecular dynamics
Bibliographic record
Abstract
We study sputtering by 100eV deuterium irradiation on deuterated amorphous carbon layers at 300K using molecular dynamics (MD) simulations. Two main results are reported here. First, a special mechanism for carbon release—additional to and distinct from the standard definitions for physical and chemical sputtering of carbon by hydrogen isotopes—has been identified and quantified. This process, here termed ion induced release of unsaturated hydrocarbons (IRUH’s), is primarily due to a recently identified atomic collision process where momentum from an impacting particle is transferred approximately perpendicular to the C–C bond, severing it. For the prescribed conditions, the IRUH yield has been found to be comparable to that of standard physical and chemical sputtering, the former being also consistently and simultaneously calculated here. IRUH release of single C atoms does not involve any hydrogenic chemistry and is therefore properly considered to be a distinct and additive type of physical sputtering to that of standard physical sputtering. For 100eV D+ the single C yields of the two physical sputtering mechanisms have been found to be approximately equal. IRUH release of carbon is directly from the surface region of the solid and is separate from, and additional to, standard chemical sputtering (not included in these MD calculations), which typically produces saturated hydrocarbons such as CD4, from regions extending over the stopping depth of the deuteron in the solid. IRUH is evidently included in experimental measurements of total sputtering yield, e.g., by weight loss. The average energy of IRUH carbon products is about 1eV and the angular distribution is consistent with a cosine distribution. Second, it is found that for the standard physically sputtered single C atoms the energy distribution is roughly consistent with the widely used Thompson distribution—this despite the fact that the assumptions on which the Thompson distribution is based are not satisfied for 100eV D on C. The angular distribution of the standard physically sputtered single C atoms is also found to be consistent with the usually assumed cosine distribution.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".