HIGHLY UNDERSATURATED ANIONS IN THE CRYSTAL STRUCTURE OF ANDYROBERTSITE - CALCIO-ANDYROBERTSITE, A DOUBLY ACID ARSENATE OF THE FORM K (Cd,Ca) [Cu2+5 (AsO4)4 ] (H2O)2
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Bibliographic record
Abstract
The crystal structure of andyrobertsite, ideally K Cd [Cu 2+ 5 (AsO 4 ) 4 {As(OH) 2 O 2 }] (H 2 O) 2 , monoclinic, a 9.8102(9), b 10.0424(6), c 9.9788(7) A, β 101.686(7)°, V 962.6(1) A 3 , P 2 1 / m , Z = 2, has been solved by direct methods and refined to an R index of 2.3% for 2140 observed ( F o > 5σ F ) reflections measured with Mo K α X-radiation. There are three crystallographically distinct As sites, each occupied by As 5+ in tetrahedral coordination. One of the As sites is coordinated by two O atoms and two (OH) groups to form a doubly acid arsenate group, {As(OH) 2 O 2 }. There are four crystallographically distinct Cu sites, each occupied by Cu 2+ in square-pyramidal coordination. There is one crystallographically distinct M site occupied by Cd, Ca and Mn 2+ coordinated by four O atoms and two (H 2 O) groups in a trigonal-prismatic arrangement. Variation in the occupancy of this site gives rise to the two related species andyrobertsite (Cd dominant) and calcio-andyrobertsite (Ca dominant). There is one distinct K site occupied by K and coordinated by four O atoms, two (OH) groups and two (H 2 O) groups in a distorted-cube arrangement. Four (CuO 5 ) polyhedra link to a central anion to form a [Cu 4 O 13 ] group. The anions at the base of this group corner-share to four (AsO 4 ) tetrahedra that link to a fifth (CuO 5 ) square pyramid. A single (Asϕ 4 ) (ϕ: unspecified anion) tetrahedron links to the central anion of the [Cu 4 O 13 ] group to form a [Cu 5 (AsO 4 ) 4 (Asϕ 4 ) O 9 ] cluster. These clusters are arranged at the vertices of non-coplanar 4 4 nets parallel to (100) and corner-link to form a heteropolyhedral framework with interstitial M (= Cd, Ca, Mn 2+ ) and K (= K) sites between adjacent 4 4 nets. Two of the anions in the structure show anomalously low incident-bond-valence sums (1.60 and 1.69 vu : valence units).
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 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) | 0.002 | 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 it