Magnesium coordination environments in glasses and minerals: New insight from high-field magnesium-25 MAS NMR
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Bibliographic record
Abstract
A comparison of 25Mg magic angle spinning (MAS) NMR spectra of crystalline and glassy diopside (CaMgSi2O6) reveals that the chemical shift in the disordered phase corresponds to that of the mineral, suggesting that sixfold coordination is essentially retained upon vitrification. Likewise, a crystalline leucite analogue (K2MgSi5O12) known to possess fourfold-coordinated Mg has the same peak position as the corresponding glass. In addition to being a sensitive probe of local structure by analogy with crystalline phases, these data may be understood in terms of the effect of competing cation field strengths: competing network modifier cations with higher field strength induce higher magnesium coordination numbers, with a consequent increase in bond length and decrease in chemical shift. This work demonstrates the utility of NMR at 14.1 Tesla for probing the coordination environment of Mg in glasses and minerals, and suggests great potential for high-field NMR investigations of quadrupolar nuclides with low resonance frequencies in amorphous systems.
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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 | 0.000 | 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) | 0.002 | 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