Structures and Physical Properties of New Semiconducting Polyselenides Ba<sub>2</sub>Cu<sub>δ</sub>Ag<sub>4</sub><sub>-</sub><sub>δ</sub>Se<sub>5</sub> with Unprecedented Linear Se<sub>3</sub><sup>4</sup><sup>-</sup> Units
Bibliographic record
Abstract
The title compounds were prepared from the elements in evacuated silica tubes at 650 degrees C, followed by slow cooling. Ba2Ag4Se5 forms a new structure type, space group C2/m, with a=16.189(2) A, b=4.5528(6) A, c=9.2500(1) A, beta=124.572(3) degrees, and V=561.4(1) A3 (Z=2). A maximum of 44% of the Ag atoms may be replaced with Cu atoms without changing the structure type. The crystal structure is composed of Ag4Se(5)4- layers, interconnected via the Ba2+ cations. The Ag atoms show irregular [3+1] coordination by the Se atoms, and the Ba atoms are located in capped square antiprisms formed by Se atoms. Most intriguing is the unprecedented occurrence of linear Se(3)4- units. According to the formulation (Ba2+)2(Ag+)4Se(3)4-(Se2-)2, this selenide is electron-precise with eight positive charges equalizing the eight negative charges. Electronic structure calculations indicated the presence of a band gap, as was experimentally confirmed: the electrical conductivity measurement revealed a gap of 0.6 eV for Ba2CuAg3Se5.
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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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".