Dihydrogen Bonding in Compressed Ammonia Borane and Its Roles in Structural Stability
Bibliographic record
Abstract
Theoretical structure prediction calculations have revealed that the conformation of ammonia borane (NH 3 BH 3 ) in the crystalline state can be modified by pressure, changing from the staggered configuration at low pressure to an eclipsed geometry at high pressure. At low pressure, the crystalline structure is stabilized by the charge transfer N—H δ+ ··· δ− H—B dihydrogen interactions. In the high pressure polymorphs, the NH 3 BH 3 is predicted to form a layered structure. The N—H δ+ ··· δ− H—B bonding is still predominant within the layer. The stacking of the layers, however, is determined by the occurrence of additional homopolar B—H δ− ··· δ− H—B interaction unprecedented in NH 3 BH 3 and facilitated by the eclipsed conformation. This bonding is shown to be the result of secondary interactions between BH 3 groups from molecules of adjacent layers. Topological analysis of the charge density and perturbation calculations on the molecule fragments show unambiguously that the B—H δ− ··· δ− H—B interaction is covalent in nature with the bond strength comparable to a conventional hydrogen bond.
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".