The crystal structure of khinite and polytypism in khinite and parakhinite
Bibliographic record
Abstract
Abstract The crystal structure of khinite, Pb2+Cu2+3Te6+O6(OH)2, orthorhombic, a = 5.7491(10), b = 10.0176(14), c = 24.022(3) Å, V = 1383.6(4) Å3, space group Fdd2, Z = 8, Dcalc = 6.29 g/cm3, from the Empire mine, Tombstone, Arizona, USA, has been solved by direct methods and refined to R1 = 3.2% on the basis of 636 unique observed reflections. There is one distinct Te site occupied by Te and coordinated by six O atoms in an octahedral arrangement with a distance of 1.962 Å. typical of Te6+. There are three octahedrally-coordinated Cu sites, each of which is occupied by Cu2+ with distances of 2.132, 2.151 and 2.308 Å, respectively. Each Cu octahedron shows four short meridional bonds (~1.95 Å) and two long apical bonds (2.46–2.99 Å) characteristic of Jahn-Teller-distorted Cu2+ octahedra. There is one distinct Pb site occupied by Pb and coordinated by six O atoms and two (OH) groups with a distance of 2.690 Å. TeF6 and CuΦ6 octahedra share edges and corners to form an [MΦ2] (where Φ = O, OH) layer of composition [TeCu3Φ8]. These layers stack along the c axis at 6 A intervals with Pb atoms between the layers. Identical layers occur in the structure of parakhinite, Pb2+Cu2+Te6+O6(OH)2, hexagonal, a = 5.765(2), c = 18.001(9) Å, V =518.0(4) Å3, space group P32, Z = 3, Dcalc = 6.30 g/cm3. It is only the relative stacking of the TeCu3Φ8 layers in the c direction that distinguishes the two structures, and hence khinite and parakhinite are polytypes.
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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 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".