A First-Principle Study of Chain Propagation Steps in the Fischer−Tropsch Synthesis on Fe(100)
Bibliographic record
Abstract
We presented density functional theory based calculations on the formation and reactivity of C 3 species produced from CO and H 2 over Fe(100). The results indicated that the conversion of syngas to propylene and propane is overall exothermic, and the most stable C 3 surface species are CCCH 2 and CCCH 3 . It was found that the chain propagation on Fe(100) is initiated by the recombination of C and CCCH 2 /CCCH 3 rather than by the coupling reaction of surface vinyl and methylene. The potential energy surface associated with such an alkynyl mechanism has been computed and validated. Furthermore, this alkynyl mechanism has been compared to the conventional alkenyl mechanism in explaining the experimental observations of the 13 C 2 H 4 -probed polymerization over Fe. It was finally found that the two propylene isotopomers observed experimentally in the product mixture are produced from surface ethylene along different reaction paths rather than the isomerization of surface allyl.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".