Structural trends for celestite (SrSO4), anglesite (PbSO4), and barite (BaSO4): Confirmation of expected variations within the SO4 groups
Bibliographic record
Abstract
The crystal structures of the isostructural orthorhombic sulfates celestite (SrSO 4 ), anglesite (PbSO 4 ), and barite (BaSO 4 ) were refined by Rietveld methods using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data. Their structural model was refined in space group Pbnm. The unit-cell parameters are a = 6.87032(3), b = 8.36030(5), c = 5.34732(1) Å, and V = 307.139(3) Å 3 for SrSO 4 ; a = 6.95802(1), b = 8.48024(3), c = 5.39754(1) Å, and V = 318.486(1) Å 3 for PbSO 4 ; and a = 7.15505(1), b = 8.88101(3), c = 5.45447(1) Å, and V = 346.599(1) Å 3 for BaSO 4 . The average [12] distances are 2.827(1), 2.865(1), and 2.953(1) Å for SrSO 4 , PbSO 4 , and BaSO 4 , respectively, and their corresponding average [4] distances are 1.480(1), 1.477(3), and 1.471(1) Å. The geometrical features of the SO 4 and MO 12 polyhedra become more symmetrical from SrSO 4 to BaSO 4 . Across the series, the a, b, and c parameters vary non-linearly with increasing V. The radii of the M 2+ cations, r M , [12], and [4] distances vary linearly with V. These structural trends arise from the effective size of the M 2+ cation (r M : Sr < Pb < Ba) that is coordinated to 12 O atoms.
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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 | 0.001 |
| 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".