Chiral Crystals of an Achiral Molecule Exhibit Plastic Bending and a Crystal-to-Crystal Phase Transition
Bibliographic record
Abstract
The achiral molecule 2-cyano-4,6-dimethylpyrimidine (Me 2 pmCN) meets simple criteria that predict a supramolecular arrangement capable of exhibiting plastic bending. Indeed, crystals grown by sublimation bend readily without breaking under manual manipulation at room temperature. Compression of a crystal perpendicular to the bending direction easily “squashes” the crystal, a mechanical response akin to metal-like malleability. Single crystal X-ray diffraction (XRD) study reveals net alignment of the molecular dipoles propagating along the 2 1 screw axis in the monoclinic space group P 2 1 . Columnar π-stacked arrays of the planar molecules extend in [100], the long axis of the crystals. Weak interactions between the columnar structures account for the observed mechanical behavior. Variable temperature powder XRD and differential scanning calorimetry measurements of the plastic crystals indicate a solid-to-solid phase transition from one crystalline phase to another at 80.7 °C prior to melting at 83.3 °C.
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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".