A new rare earth disilicate (REE <sub>2</sub> Si <sub>2</sub> O <sub>7</sub> ; REE = Dy, Tm, Lu; type-L): Evidence for non-quenchable 10 GPa polymorph with silicon in fivefold trigonal bipyramidal coordination?
Why this work is in the frame
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Bibliographic record
Abstract
A new structure type (L) is reported for disilicates of the middle and heavy rare earth elements (REE) quenched from 10 GPa, 1600-1700 °C. Crystal data are: triclinic, space group P1̅ , Z = 6; Dy2Si2O7: a = 6.5971(3), b = 6.6504(2), c = 18.0582(6) Å, α = 83.791(2), β = 88.653(2), γ = 88.498(2)°, V = 787.2 Å3, and Dx = 6.242 g/cm3; Tm2Si2O7: a = 6.5499(2), b = 6.5876(2), c = 17.8916(7) Å, α = 83.828(1), β = 88.368(1), γ = 88.152(2)°, V = 766.9 Å3, and Dx = 6.574 g/cm3; Lu2Si2O7: a = 6.5240(2), b = 6.5553(2), c = 17.7909(6) Å, α = 83.977(2), β = 88.074(2), γ = 87.846(2)°, V = 755.8 Å3, and Dx = 6.830 g/cm3. The type-L structure comprises linear trisilicate [Si3O10]8- and orthosilicate [SiO4]4- ions cross linked by REE3+ in one sevenfold and five eightfold coordinated positions (to 3.0 Å), and is assembled from alternating (001) strips of the type-B structure of REE2Si2O7 and a sheared structure containing structural elements found in the type-B structure but with Si distributed with 50% occupancy over two face-sharing tetrahedra. The geometry of these half-occupied tetrahedra is consistent with decomposition of a SiO5 trigonal bipyramid during quenching of the pressure.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 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 it