THE CRYSTAL STRUCTURE OF BERGENITE, A NEW GEOMETRICAL ISOMER OF THE PHOSPHURANYLITE GROUP
Bibliographic record
Abstract
The crystal structure of bergenite, ideally Ca2Ba4[(UO2)3O2(PO4)2]3(H2O)16, monoclinic, space group P21/c, a 10.092(1), b 17.245(2), c 17.355(2) Å, 113.678(2)°, V 2766.2(3) Å3, Z = 2, Dcalc 4.82 g/cm3, was solved by direct methods and refined by full-matrix least-squares techniques on the basis of F2 to agreement indices R1 of 5.0 % calculated for 4118 unique observed reflections (|Fo | ≥ 4F), and wR2 of 11.9 % for all data. Intensity data were collected at room temperature using MoK radiation and a CCD-based area detector. The structure of bergenite contains five symmetrically independent uranium atoms, each of which is part of a (UO2)2+ uranyl ion. The uranyl ions of U(1), U(2) and U(3) are coordinated by five additional ligands giving pentagonal bipyramids, and the uranyl ions of U(4) and U(5) are coordinated by six additional ligands yielding hexagonal bipyramids. The uranyl pentagonal bipyramids share edges, forming dimers, which are linked to uranyl hexagonal bipyramids on either side, resulting in chains of bipyramids. Each uranyl hexagonal bipyramid shares two equatorial edges with phosphate tetrahedra, and the resulting uranyl phosphate chains are linked into sheets by the sharing of vertices of phosphate tetrahedra with uranyl pentagonal bipyramids of adjacent chains. The uranyl phosphate sheet in bergenite is a new geometrical isomer of the phosphuranylite group; the phosphate tetrahedra between the uranyl chains vary orientations in an up-up-down up-up-down (uuduud) pattern, and the pairs of tetrahedra attached to uranyl hexagonal bipyramids change orientations in a complementary same-same-opposite (SSO) manner (symbol uuduudSSO). In bergenite, the uranyl phosphate sheets are oriented parallel to (¯102),
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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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".