The crystal structure of ammoniojarosite, (NH<sub>4</sub>)Fe<sub>3</sub>(SO<sub>4</sub>)<sub>W</sub>(OH)<sub>6</sub>and the crystal chemistry of the ammoniojarosite–hydronium jarosite solid-solution series
Bibliographic record
Abstract
Abstract The atomic structure of ammoniojarosite,[(NH4)Fe3(SO4)2(OH)6], a = 7.3177(3) Å, c = 17.534(1) Å, space groupR m,Z= 3, has been solved using single-crystal X-ray diffraction (XRD) towR3.64% and R 1.4%. The atomic coordinates of the hydrogen atoms of the NH4group were located and it was found that the ammonium group has two different orientations with equal probability. Hydronium commonly substitutes into jarosite group mineral structures and samples in the ammoniojarosite–hydronium jarosite solid-solution series were synthesized and analysed using powder XRD and Rietveld refinement. Changes in unit-cell dimensions and bond lengths are noted across the solidsolution series. The end-member ammoniojarosite synthesized in this study has no hydronium substitution in theAsite and the unit-cell dimensions determined have a smaller a dimension and larger c dimension than previous studies. Two natural ammoniojarosite samples were analysed and shown to have similar unit-cell dimensions to the synthetic samples. Short-wave infrared and Fourier transform infrared spectra were collected for samples from the NH4–H3O jarosite solid-solution series and the differences between the end-members were significant. Both are useful tools for determining NH4content in jarosite group minerals.
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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".