Franconite, NaNb<sub>2</sub>O<sub>5</sub>(OH)·3H<sub>2</sub>O: structure determination and the role of H bonding, with comments on the crystal chemistry of franconite-related minerals
Bibliographic record
Abstract
Abstract The crystal structure of franconite, NaNb 2 O 5 (OH)·3H 2 O, has been characterized by single-crystal X-ray diffraction using material from Mont Saint-Hilaire, Québec, Canada. Results give a = 10.119(2), b = 6.436(1), c = 12.682(2) Å and β = 99.91(3)° and confirm the correct space group as P 2 1 / c . The crystal structure, refined to R = 4.63% and wR 2 =11.95%, contains one Na site, two distorted octahedral Nb sites and nine O sites. It consists of clusters of four edge-sharing Nb(O,OH) 6 octahedra, linked through shared corners to adjacent clusters, forming layers of Nb(O,OH) 6 octahedra. These alternate along [100] with layers composed of NaO(H 2 O) 4 polyhedra, the two being linked together by well defined H bonding. The predominance of H bonding, essential to the mineral, results in a perfect {100} cleavage. Chemical analyses ( n = 7) of four crystals give the empirical formula (Na 0.73 Ca 0.13☐0.14 ) ∑=1.00 (Nb 1.96 Ti 0.02 Si 0.02 Al 0.01 ) ∑=2.01 O 5 (OH)·3H 2 O (based on nine oxygens) or ideally NaNb 2 O 5 (OH)·3H 2 O. Franconite is crystallo-chemically related to SOMS [Sandia Octahedral Molecular Sieves; Na 2 Nb 2− x MxO 6− x (OH) x ·H 2 O with M = Ti, Zr, Hf], a group of synthetic compounds with strong ion-exchange capabilities. Both hochelagaite (CaNb 4 O 11 · n H 2 O) and ternovite (MgNb 4 O 11 · n H 2 O) have X-ray powder diffraction patterns and cation ratios similar to those of franconite indicating that these minerals probably have similar structures.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 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 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".