The role of water in the structures of synthetic hallimondite, Pb <sub>2</sub> [(UO <sub>2</sub> )(AsO <sub>4</sub> ) <sub>2</sub> ](H <sub>2</sub> O) <sub> <i>n</i> </sub> and synthetic parsonsite, Pb <sub>2</sub> [(UO <sub>2</sub> )(PO <sub>4</sub> ) <sub>2</sub> ](H <sub>2</sub> O) <sub> <i>n</i> </sub> , 0 ≤ <i>n</i> ≤ 0.5
Why this work is in the frame
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Bibliographic record
Abstract
The crystal structures of synthetic hallimondite and synthetic parsonsite have been refined by fullmatrix least-squares techniques to agreement indices (hallimondite, parsonsite) wR2 of 5.5, and 7.6% for all data, and R1 of 2.7 and 3.4%, calculated for 3391 and 3181 unique observed reflections (|Fo| ≥ 4σF), respectively. Hallimondite is triclinic, space group P1̅, Z = 2, a = 7.1153(8), b = 10.4780(12), c = 6.8571(8) Å, α = 101.178(3)°, β = 95.711(3)°, γ = 86.651(3)°, V = 498.64(3) Å3, and is isostructural with parsonsite, triclinic, space group P1 . , Z = 2, a = 6.8432(5), b = 10.4105(7), c = 6.6718(4) Å, α = 101.418(1)°, β = 98.347(2)°, γ = 86.264(2)°, V = 460.64(5) Å3. In both structures, hexavalent uranium occurs as a uranyl pentagonal bipyramid. The uranyl polyhedra share an edge, forming dimers that are linked by edge- and vertex-sharing with arsenate or phosphate tetrahedra to form chains along [001]. Two symmetrically distinct Pb positions connect the chains. In hallimondite, a partially occupied oxygen atom is located in the cavity between the uranyl arsenate chains and Pb positions, and is attributed to an H2O group. The crystal of synthetic parsonsite investigated does not have appreciable electron density at this position, but its structural cavity is large enough to contain H2O. The presence of H2O in synthetic hallimondite, and its absence in synthetic parsonsite, are supported by the results of FTIR spectroscopy. In conjunction with thermogravimetric results from the literature, we suggest that the formula of parsonsite should be considered Pb2[(UO2)(PO4)2](H2O)n, and hallimondite, Pb2[(UO2)(AsO4)2](H2O)n, with 0 ≤ n ≤ 0.5 in each case.
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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 | 0.015 | 0.007 |
| Meta-epidemiology (narrow) | 0.024 | 0.023 |
| Meta-epidemiology (broad) | 0.022 | 0.012 |
| Bibliometrics | 0.008 | 0.018 |
| Science and technology studies | 0.012 | 0.025 |
| Scholarly communication | 0.007 | 0.011 |
| Open science | 0.019 | 0.009 |
| Research integrity | 0.011 | 0.023 |
| Insufficient payload (model declined to judge) | 0.000 | 0.003 |
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