High-field multinuclear solid-state nuclear magnetic resonance (NMR) and first principle calculations in MgSO<sub>4</sub> polymorphs
Bibliographic record
Abstract
A combination of solid-state nuclear magnetic resonance (NMR) and first principles calculations was applied to obtain 17 O, 25 Mg, and 33 S NMR parameters for two polymorphs of anhydrous magnesium sulfate. Working at the very high magnetic field of 21.14 T results in a dramatic improvement of resolution through a reduction of the effects of quadrupolar interactions and significant improvement in sensitivity. Experimental 25 Mg and 33 S spectra are dominated by quadrupolar interactions with quadrupolar parameters unique for each polymorph. In the case of 17 O, there is a substantial contribution of the chemical shift anisotropy. The use of multiple-quantum magic-angle spinning (MQMAS) experiments allows the resolution of distinct oxygen species and assignment of signals in the experimental 17 O spectrum. Chemical shielding constants and quadrupolar parameters for all three nuclei were calculated using plane wave pseudopotential density functional theory as implemented in the CASTEP computational package. The calculated NMR parameters are in very good agreement with the experimental results and help in signal assignment of the 17 O spectrum. The results suggest applicability of such a combined computational and experimental solid-state NMR approach for the refinement of crystallographic data.
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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 | 0.000 | 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 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".