Association Complex Formation in Gas-Phase Ta Cluster Reactions with Simple Alkanes: Probing the Role of Entropy in Rate Determination for Barrierless Adsorption Processes
Bibliographic record
Abstract
Rate coefficients for the reactions of ethane, propane, n -butane, isobutane, and neopentane with Ta atoms and Ta clusters consisting of up to 30 Ta atoms have been measured in a fast-flow reactor. A near-monotonic dependency of the rate coefficients on cluster size is observed for each of these hydrocarbons, with the exception of Ta 11, which exhibits rate coefficients that are several times that observed for the analogous reaction with Ta 10 and Ta 12, for propane, n -butane, and isobutane. Modeling the general trend in the rate coefficients using transition state theory is found to require a relatively loose transition state with free rotation of the hydrocarbon about the bonding point on the cluster, consistent with the rate-determining step being cluster removal by an association reaction process. It is demonstrated that, in general, metal cluster reactions with reagents that can form strongly bound association complexes may exhibit little evidence of cluster-size-based selectivity in the rate of cluster removal, despite exhibiting significant selectivity in terms of the extent of the dehydrogenation reaction involved.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".