The structures of marialite ( <i>M</i> <i>e</i> <sub>6</sub> ) and meionite ( <i>M</i> <i>e</i> <sub>93</sub> ) in space groups <i>P</i> 4 <sub>2</sub> / <i>n</i> and <i>I</i> 4/ <i>m</i> , and the absence of phase transitions in the scapolite series
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Bibliographic record
Abstract
The crystal structures of marialite ( M e 6 ) from Badakhshan, Afghanistan and meionite ( M e 93 ) from Mt. Vesuvius, Italy were obtained using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and Rietveld structure refinements. Their structures were refined in space groups I 4/ m and P 4 2 / n , and similar results were obtained. The M e 6 sample has a formula Ca 0.24 Na 3.37 K 0.24 [Al 3.16 Si 8.84 O 24 ]Cl 0.84 (CO 3 ) 0.15 , and its unit-cell parameters are a =12.047555(7), c =7.563210(6) Å, and V =1097.751(1) Å 3 . The average ⟨T1-O⟩ distances are 1.599(1) Å in I 4/ m and 1.600(2) Å in P 4 2 / n , indicating that the T1 site contains only Si atoms. In P 4 2 / n , the average distances of ⟨T2-O⟩=1.655(2) and ⟨T3-O⟩=1.664(2) Å are distinct and are not equal to each other. However, the mean ⟨T2,3-O⟩=1.659(2) Å in P 4 2 / n and is identical to the ⟨T2′-O⟩=1.659(1) Å in I 4/ m . The ⟨M-O⟩ [7]=2.754(1) Å (M site is coordinated to seven framework O atoms) and M-A=2.914(1) Å; these distances are identical in both space groups. The M e 93 sample has a formula of Na 0.29 Ca 3.76 [Al 5.54 Si 6.46 O 24 ]Cl 0.05 (SO 4 ) 0.02 (CO 3 ) 0.93 , and its unit-cell parameters are a =12.19882(1), c =7.576954(8) Å, and V =1127.535(2) Å 3 . A similar examination of the M e 93 sample also shows that both space groups give similar results; however, the C–O distance is more reasonable in P 4 2 / n than in I 4/ m . Refining the scapolite structure near M e 0 or M e 100 in I 4/ m forces the T2 and T3 sites (both with multiplicity 8 in P 4 2 / n ) to be equivalent and form the T2′ site (with multiplicity 16 in I 4/ m ), but ⟨T2-O⟩ is not equal to ⟨T3-O⟩ in P 4 2 / n . Using different space groups for different regions across the series implies phase transitions, which do not occur in the scapolite series.
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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 | 0.004 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.001 | 0.004 |
| Scholarly communication | 0.000 | 0.002 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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