Crystal structure of novel high-pressure perovskite K <sub>2/3</sub> Th <sub>1/3</sub> TiO <sub>3</sub> , a possible host for Th in the upper mantle
Bibliographic record
Abstract
The high-pressure perovskite K 2/3 Th 1/3 TiO 3 was synthesized at P = 6 GPa and T = 1200 °C. This compound does not form at ambient pressures, as both solid-state reaction and synthesis from the melt yield a mixture of thorianite (ThO 2 ) and jeppeite (K 2 Ti 6 O 13 ). K 2/3 Th 1/3 TiO 3 is a partially ordered derivative of the ideal perovskite structure, which crystallizes with tetragonal symmetry, in space group P4/mmm, a = 3.9007(2), c = 7.8099(7) Å, V = 118.83(2) Å 3 , Z = 2. The structure of this compound was refined by the Rietveld method from the X-ray diffraction powder data. The degree of disorder calculated from the refined cation occupancies of the 1a and 1b sites is 58%. The K 1+ cations preferentially enter the 1a site, whereas most Th 4+ is accommodated in the comparatively smaller 1b site (polyhedral volumes are 53 and 46 Å 3 , respectively). In response to this two-dimensional (planar) ordering, the Ti 4+ cations are displaced by about 0.1 Å toward the planes populated by the lower-charged cations. K 2/3 Th 1/3 TiO 3 and related structures may be a viable repository for Th in Ti-rich alkali metasomatites in the lithospheric upper mantle.
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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".