Chemistry on a peg-board: the effect of adatom–adatom separation on the reactivity of dihalobenzenes at Si(111)7×7 surfaces
Bibliographic record
Abstract
A simple model of the thermal dihalogenation of a silicon surface by an adsorbate, Br-R-Br, is described for the first time. The model consists of a pair of silyl radicals (SiH(3)), treated by density functional theory, placed a distance d apart. Two adsorbates were considered, one with R = benzene and one with R = biphenyl. The Br...Br internuclear separation (r(Br, Br)) in 1,4-dibromobenzene is 6.6 A, whereas that in 4,4'-dibromobiphenyl is 10.9 A. In the former case the model yields a (most-favourable) 'critical' separation d* approximately 10.2 A, corresponding to the lowest-energy barrier, and in the latter case d* approximately 13.8 A. The dangling-bond separations, d, were restricted to values present at an Si(111)7 x 7 surface. The critical values, d*, exceeded the corresponding value of r(Br, Br) in the intact adsorbate in each case by ca. 3.5 A, corresponding to ca. 93% of the van der Waals molecular size. This is approximately the observed increase in separation of a pair of halogen atoms in reactions at a Si surface, as compared with the separation in the parent molecule. If the dangling bonds at the surface are too close to one another (d < d*), the adsorbate molecules' charge cloud extends too far for a favourable interaction, whereas if the dangling bonds are too far apart (d < d*) the adsorbate's charge cloud cannot reach them. When the second reagent is a peg-board, the factors governing chemical reactivity are more exposed to view.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| 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 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".