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
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) wR 2 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 (|F o | ≥ 4σ F ), 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) Å 3 , 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) Å 3 . 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 H 2 O 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 H 2 O. The presence of H 2 O 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 Pb 2 [(UO 2 )(PO 4 ) 2 ](H 2 O) n , and hallimondite, Pb 2 [(UO 2 )(AsO 4 ) 2 ](H 2 O) n , with 0 ≤ n ≤ 0.5 in each case.
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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 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 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".