A <sup>47/49</sup>Ti Solid-State NMR Study of Layered Titanium Phosphates at Ultrahigh Magnetic Field
Bibliographic record
Abstract
Layered titanium phosphates (TiPs) have many potentially important applications in ion exchange, catalysis, intercalation, and sorption. Characterization of metal local environments by solid-state 47/49 Ti NMR has been difficult due to many unfavorable 47/49 Ti NMR properties. In this work, we have directly characterized the local structures around Ti in several representative layered TiPs, including α-, β-, and γ-TiP, by examining the 47/49 Ti static NMR spectra of these materials at an ultrahigh magnetic field of 21.1 T. The 47/49 Ti chemical shielding and electric field gradient (EFG) tensors have been extracted from spectral analysis. The observed 47/49 Ti spectra are mainly determined by the second-order quadrupolar interactions. The quadrupole coupling constants ( C Q ) are sensitive to the distortion of the TiO 6 octahedron in this series of layered TiPs. Quantum mechanical calculations have been performed on several model clusters as well as periodic systems. The results indicate that, in addition to the oxygens in the first coordination sphere of Ti, the atoms in the second and third coordination spheres and beyond also have significant effects on the EFG at the metal center, and this long-range effect contributes substantially to the C Q . A relationship between observed C Q and the Ti−O bond length distortion parameter appears to exist, and this empirical correlation is also confirmed by theoretical calculations. Using sodium-exchanged α-TiP (α-Na-TiP) with an unknown structure as an example, we show that the 47/49 Ti NMR spectra can provide partial information on the local environment of the metal center. For this material, the ion exchange does not affect the Ti local environment significantly. It appears that the layer in α-TiP is more robust compared to that of the zirconium analogue.
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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".