Sodium hydrogencarbonate (NaHCO3): coincidence-site lattice twinning and structure refinement
Bibliographic record
Abstract
Sodium hydrogencarbonate (NaHCO3) has been recrystallised hydrothermally using a cooling ramp from 250 °C to 190 °C at 0.069 GPa, and investigated by single crystal X-ray diffraction at room temperature and pressure. Representative crystal data are: monoclinic, space group P21/n, Z = 4, a = 7.4688(4), b = 9.6842(6), c = 3.4791(2) Å, β = 93.321(2)°, R = 0.026, and Dx = 2.221 g/cm3. The crystals investigated are complexly twinned by reticular pseudomerohedry, but give two coincidence-site lattices with pseudocell parameters: a = 3.4791(2), b = 9.6842(6), c = 29.875(2) Å, β = 93.321(2)°, twin axis [001], twin index (Σ) = 4; and, a = 8.4360(6), b = 9.6811(7), c = 24.941(2) Å, β = 99.109(5)°, twin axis [10-1], Σ = 8. The Σ = 4 and Σ = 8 twins occur in separate twinned crystals but in similar twin proportions (5.5 : 1), and are most likely secondary in origin. The two coincidence-site lattices are permitted in NaHCO3 because β corresponds closely to the theoretical value given by the positive root of [sin2 (β – π/2) = 3/912].
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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) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.002 |
| 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 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".