The Role of Dynamic Polyhedral Rotations in the Phase Transitions of Rb<sub>3</sub>AlF<sub>6</sub> and Cs<sub>3</sub>AlF<sub>6</sub>
Bibliographic record
Abstract
The structures and phase transitions of cryolite-related rubidium and cesium aluminum fluoride phases are investigated and related to the dynamic motions of AlF 6 octahedra. Low-temperature synchrotron powder diffraction data were collected on Rb 3 AlF 6 and Cs 3 AlF 6 to search for new polymorphs, and MAS NMR was used to study changes in dynamic motion occurring across the phase transitions. Rb 3 AlF 6 is found to undergo a subtle phase transition around 270 K and then a second, more substantial phase transition around 250 K. The low temperature polymorphs maintain essentially the same framework as the room temperature Fddd structure, but are more complex due to an ordered freezing of dynamic rotations of AlF 6 octahedra. Freezing of octahedral rotations is observed in Cs 3 AlF 6 around room temperature, but the same C 2/ m structure is maintained down to 80 K without any phase transitions. The dynamic motions and local structure in the high-temperature cubic polymorph of Cs 3 AlF 6 are also examined jointly by MAS NMR and reverse Monte Carlo modeling of X-ray pair distribution function data.
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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) | 0.001 | 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".