THE CRYSTAL STRUCTURE OF SYNTHETIC KUTINAITE, Cu14Ag6As7
Bibliographic record
Abstract
The crystal structure of synthetic kutinaite, Cu14Ag6As7, was determined from powder-diffraction data recorded on a Guinier diffractometer and refined by Rietveld method with the program FULLPROF. The final refinement (/max < 0.2) with 31 (9 profile and 23 structural) parameters using 4600 data points and 226 reflections yielded the following agreement indices: Rwp = 18.2%, Rp = 13.4%, Rexp = 14.7%, S = 1.54, R(B) = 1.78%. The cubic structure has a equal to 11.78079(2) Å (standard uncertain-ties are underestimated by a score-factor of 2.4686) and space group Pm¯3m, Z = 4. Apart from partially ordered Cu vacancies, the arrangement of atoms is very close to that in Fm¯3m. The Pm¯3m structure of kutinaite is a result of the frozen-in partial order of Cu vacancies which, in a presumed high-temperature Fm¯3m structure, should be completely disordered. The atoms Cu2 and Cu3 are tetrahedrally coordinated by As, the atoms Cu1 and Cu4 (with partial occupancies) have trigonal planar As coordination. Atoms of Ag form octahedral Ag6 clusters in octahedral cavities of the Cu–As framework. On the one hand, the structure of kutinaite contains a multitude of short metal–metal and metal–semimetal contacts, resulting in high coordination-numbers and indicating direct metal–metal interactions. The presence of metal–metal bonding contacts is supported by an electron-density analysis, which gives the following bonding contact limits: 2.70 Å (Cu–Cu), and 3.05 Å (Ag–Cu). On the other hand, a network of important Cu–As bonds forms a three-dimensional complex with a nominal net negative charge balanced by nominal positive charges of localized Ag6 complexes. This situation results in two complementary descriptions of the structure of kutinaite: kutinaite
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".