ATHENEITE, [Pd2][As0.75Hg0.25], FROM ITABIRA, MINAS GERAIS, BRAZIL: CRYSTAL STRUCTURE AND REVISION OF THE CHEMICAL FORMULA
Bibliographic record
Abstract
The crystal structure of the rare mineral atheneite was solved using intensity data collected from a crystal from Itabira, Minas Gerais, Brazil. The structure is hexagonal, space group P 62 m, with a = 6.813(1), c = 3.4892(5) A and V = 140.26(4) A 3 . The refinement of an anisotropic model led to an R index of 7.26% for 261 independent reflections. The crystal structure strongly resembles that of synthetic MM’As compounds, with M = Ru, Rh, Pd, and M = 3 d transition element. There are two fully occupied Pd sites: site Pd1 has a ten-fold coordination, and Pd2, an eleven-fold coordination. The two As atoms in the structure have a tricapped trigonal prismatic coordination; As1 is filled by arsenic only, whereas As2 has an occupancy of 0.60 As and 0.40 Hg. The presence of Hg at the As2 site accounts for the longer distances observed. On the basis of information gained from this characterization, the crystal-chemical formula was revised according to the structural results, yielding Pd 2 [As 0.75 Hg 0.25 ] ( Z = 3) instead of (Pd,Hg) 3 As ( Z = 2) as previously reported. A recalculation of the chemical data listed in the scientific literature for atheneite according to the structural results obtained here leads to an excellent agreement.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| 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 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".