Structural variations across the nepheline (NaAlSiO4)–kalsilite (KAlSiO4) series
Bibliographic record
Abstract
Abstract The crystal structures of 19 samples from the nepheline (NaAlSiO4; Ne)–kalsilite (KAlSiO4; Ks) series, previously prepared via ion-exchange, were examined using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and Rietveld structure refinements. Parent materials for the three series include a natural Monte Somma nepheline (series-1), synthetic Na nepheline (series-2), and high-Si synthetic nepheline (series-3), having excess Si mole percentages of 5.2, 1.7, and 12.5%, respectively. Three different structure-types were found to occur among the samples examined: nepheline (P63), tetrakalsilite (P63), and kalsilite (both P63 and P31c intergrowth). Trikalsilite was not observed in this study. Vacancies (☐) at the K site as well as Ca and K atoms at the Na1 site play an important role in the crystal-chemical behavior of nepheline solid solutions. Vacancies cause an elongation in the average <K-O>[9] distance in nepheline. When K atoms enter the Na1 site in nepheline, the average <(Na,K)-O>[7] distance increases linearly and is parallel to the average <(Na,K)-O>[9] distance in kalsilite and the grand mean of such distances in trikalsilite and tetrakalsilite. Before K atoms enter the Na1 site, the average <(Na,K)-O>[7] distance is constant because of the full occupancy of the Na1 site with Na atoms. Ca atoms at the Na1 site in the Monte Somma sample-1 cause a contraction in the <(Na,K)-O>[7] distance. In Na-rich nepheline samples, Na atoms in the large channels occupy a Na(K) site that is off the 63 axis and close to the usual K site. In natural nepheline samples, the K site in most cases contains K atoms and ☐, and the Na1 site is filled mainly with Na, minor Ca, and K atoms in K-rich samples. Nepheline from Monte Somma (sample-1) contains weak satellite reflections that are also present in some other kalsilite samples. Average <T-O> distances indicate a high degree of Al-Si disorder in nepheline but increasing Al-Si order in tetrakalsilite and kalsilite. Increasing the amount of K atoms beyond the ideal composition of K0.25Na0.75[AlSiO4] causes expansion in multiple structural parameters because of the larger size of K+ relative to Na+.
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How this classification was reachedexpand
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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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 teacher head, 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".