SYNTHESIS AND CRYSTAL STRUCTURE OF A NEW Pb URANYL OXIDE HYDRATE WITH A FRAMEWORK STRUCTURE THAT CONTAINS CHANNELS
Bibliographic record
Abstract
Using lead oxide, uranyl nitrate and ultrapure water, seven hydrothermal synthesis experiments were performed with Pb:U molar ratios ranging from 1:1 to 1:10. Reaction products were characterized by powder and single-crystal X-ray diffraction. Two novel Pb uranyl oxide hydrates were found, with structural formulae Pb2(H2O)[(UO2)10UO12(OH)6(H2O)2] and Pb0.5[(UO2)4O2(OH)5](H2O)4 (Pb-poor fourmarierite). The synthesis products are related to the Pb:U molar ratio of the solution, and indicate a trend from curite, Pb3+x(H2O)2[(UO2)4O4+x(OH)3–x]2, to Pb2(H2O)[(UO2)10UO12(OH)6(H2O)2], then to Pb0.5[(UO2)4O2(OH)5](H2O)4 with decreasing Pb in the solution. The structure of Pb2(H2O)[(UO2)10UO12(OH)6(H2O)2], Z = 4, monoclinic, space group C2/c, a 13.281(5), b 10.223(4), c 26.10(1) Å, 103.202(6)°, V 3450(2) Å3, was solved by direct methods and refined on the basis of F2 using 4065 unique reflections. The agreement index (R1) was 6.38%, calculated for 1306 unique observed reflections (|Fo | ≥ 4F). The structure contains complex chains of edge- and vertex-sharing uranyl pentagonal and square bipyramids, as well as distorted U6+O6 octahedra, along both the [110] and [¯110] directions. The chains in the two orientations are linked at z ≈ 0.25 and z ≈ 0.75, forming a framework that contains elongate open channels. The Pb2+ cations occur in the channels between adjacent chains.
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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 | 0.000 |
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 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".