Relating <sup>139</sup>La Quadrupolar Coupling Constants to Polyhedral Distortion in Crystalline Structures
Bibliographic record
Abstract
A broad series of crystalline lanthanum oxide-based materials has been investigated through high-field 139 La solid state nuclear magnetic resonance (ssNMR) spectroscopy and ab initio density functional theory (DFT) calculations. The 139 La NMR spectra of LaBGeO 5, LaBSiO 5, LaBO 3, LaPO 4 ·1.8H 2 O, La 2 (SO 4 ) 3 ·9H 2 O, and La 2 (CO 3 ) 3 ·8H 2 O are reported for the first time. Both newly reported and literature values of 139 La quadrupolar coupling constants ( C Q ) are related to various quantitative expressions of polyhedral distortion, including sphericity (Σ) and ellipsoid span (ϵ). The compounds were separated into two groups based upon their polyhedral distortion behavior: compounds with the general formula LaMO 3, where M is a trivalent cation; compounds with different general formulas. The 139 La C Q of the LaMO 3 family was found to correlate best with ϵ. The 139 La C Q of non-LaMO 3 compounds correlates adequately to ϵ but is better described by Σ. The 139 La isotropic chemical shift (δ iso CS ) of the non-LaMO 3 compounds is negatively correlated with the lanthanum coordination number; there is insufficient data from the LaMO 3 compounds to draw conclusions relating to chemical shift. DFT calculations of NMR parameters prove to be a sensitive probe of the quality of input geometry, with predicted parameters agreeing with experiment except in cases where the crystal structure is suspect.
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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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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".