Influence of F content on the composition of Al-rich synthetic phlogopite: Part II. Probing the structural arrangement of aluminum in tetrahedral and octahedral layers by <sup>27</sup> Al MQMAS and <sup>1</sup> H/ <sup>19</sup> F- <sup>27</sup> Al HETCOR and REDOR experiments
Bibliographic record
Abstract
The influence of F substitution on the local structure of Al in the tetrahedral and octahedral sheets of synthetic Al-rich phlogopite samples with nominal gel compositions of K(Mg 3-x Al x )[Al 1+x Si 3-x O 10 ] (OH) y (F) 2-y between 0.0 ≤ x ≤ 0.8 and 0.5 ≤ y ≤ 1.8, was studied by 27 Al MAS, MQMAS, { 1 H/ 19 F} → 27 Al 2 D CPMAS (HETCOR) and { 1 H/ 19 F} 27 Al REDOR solid-state NMR and by IR spectroscopy. Changes in intensity of the absorption bands in the OH-stretching region of the IR spectra clearly indicate the incorporation of octahedral Al. Signals from the different phases can be separated in the 27 Al MQMAS NMR spectra by generation of an isotropic dimension in F1. The 27 Al quadrupolar parameters of the four phases were estimated from 27 Al MAS NMR spectra obtained at 104.26 and 208.42 MHz. The quadrupolar coupling constant and isotropic chemical shift increases with increasing Al content for the IV Al site in phlogopite. The VI Al site shows a clear increase of the asymmetry parameter and C Q with increasing F content. The estimated 27 Al signal areas show the lowest amount of impurity phases at high OH contents and a stabilization of VI Al sites by hydroxyl groups. The {1H} → 27 Al 2D CPMAS (HETCOR) NMR experiment at short contact times provides information about site neighborhoods of tetrahedral Al sites and Mg 3 OH as well as Mg 2 AlOH sites, whereas magnetization is only transferred to the octahedral Al sites from hydroxyl groups in Mg 2 AlOH sites. The { 19 F} → 27 Al 2D CPMAS (HETCOR) NMR spectrum is dominated by IV Al sites coupled to the Mg 3 F complex in phlogopite. Resonances from Mg 2 AlF complexes are not observed. Finally, the { 1 H/ 19 F} 27 Al REDOR experiments support the results of the 2D CPMAS (HETCOR) experiments.
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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".