Multinuclear NMR Study of Zinc Dicyanide
Bibliographic record
Abstract
Abstract The isotropic negative expansion of Zn(CN)2 has been linked to a temperature induced increase in off-axis tilting of the C–N bond direction and an increase in CN-bond length. However, the bond length could be determined only indirectly based on pair-distribution function analysis and was found to be surprisingly large. Here we study Zn(CN)2 by nuclear magnetic resonance spectroscopy and first principles calculations. By using samples enriched in 13 C and 15 N the dipole coupling between carbon and nitrogen is determined, and from this an upper bound on the C–N bond length of 1.19 ± 0.01 Å is derived. This quantity agrees with earlier determinations based on diffraction but is shorter than estimates based on pair distribution function analysis. The relation of this estimate to possible dynamics in the sample is discussed. Finally, 67 Zn NMR is used together with first principles calculations to assess disorder in the material.
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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 | 0.000 |
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".