Correlation between AO<sub>6</sub> Polyhedral Distortion and Negative Thermal Expansion in Orthorhombic Y<sub>2</sub>Mo<sub>3</sub>O<sub>12</sub> and Related Materials
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Bibliographic record
Abstract
The Pbcn orthorhombic phase of Y 2 Mo 3 O 12 has been examined through high-resolution X-ray powder diffraction (10−450 K), heat capacity determination (2−390 K), and differential scanning calorimetry (103−673 K). No phase transition was found over this temperature range. The overall thermal expansion is negative, and the average linear thermal expansion coefficient, α l, is −9.02 × 10 −6 K −1 averaged over T = 20−450 K. From a thorough analysis of the structure of Y 2 Mo 3 O 12, we find that the YO 6 octahedra and MoO 4 tetrahedra are increasingly distorted with increasing temperature. The inherent volume distortion parameter (υ) of A O 6 has been introduced to quantitatively evaluate polyhedral distortion and it is observed that this parameter is strongly correlated with the linear coefficient thermal expansion (α l ) of different members of the A 2 M 3 O 12 family. We attribute the negative thermal expansion to the reduction of the mean Y−Mo nonbonded distances and Y−O−Mo bond angles with increasing temperature, the joint action of high-energy optical and low-energy translational and librational modes.
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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 | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| 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 it