Combined <sup>135/137</sup>Ba Solid-State NMR at an Ultrahigh Magnetic Field and Computational Study of β-Barium Borate
Bibliographic record
Abstract
β-Barium Borate (β-BBO or β-BaB 2 O 4 ) is an important nonlinear optical material with many practical applications. In this work, we have directly probed the local Ba environment in β-BBO by acquiring static 135 Ba and 137 Ba solid-state NMR spectra at an ultrahigh magnetic field of 21.1 T. The observed spectra are completely dominated by the second-order quadrupolar interaction. The measured quadrupolar coupling constants are 14.9 and 22.8 MHz for 135 Ba and 137 Ba, respectively. A computational study of the electric field gradient tensor at Ba 2+ was also performed using both plane-wave pseudopotentials (CASTEP) and ab initio (Gaussian 03) methods. Combining the experimental and theoretical results allows one to shed some light on the controversy regarding the true space group of β-BBO. We conclude that the space group R 3 c represents the true structure of β-BBO rather than does the space group R 3. This work demonstrates that a combination of 135/137 Ba NMR and theoretical calculations is a useful tool for characterization of Ba-containing materials with unknown or poorly described structures.
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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 | 0.001 | 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 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".