Quaternary Rare-Earth Oxyselenides <i>RE</i><sub>4</sub>Ga<sub>2</sub>Se<sub>7</sub>O<sub>2</sub> (<i>RE</i> = Pr, Nd) with Trigonal Bipyramidal GaSe<sub>5</sub> Units: Evaluation of Optical, Thermoelectric, and Electrocatalytic Properties
Bibliographic record
Abstract
Phase-pure samples and single crystals of the rare-earth oxyselenides RE 4 Ga 2 Se 7 O 2 ( RE = Pr, Nd) were prepared by reactions at 950 °C. They adopt a new structure type (orthorhombic, space group Pnma, a = 11.721(2)–11.683(2) Å, b = 3.9882(7)–3.9667(7) Å, c = 29.644(5)–29.581(5) Å, Z = 4) consisting of RE Se 6 trigonal prisms, GaSe 4 tetrahedra, and GaSe 5 trigonal bipyramids linked to form corrugated layers between which strips of edge-sharing RE 4 O tetrahedra are inserted. The bonding character is mostly ionic within RE –O and RE –Se blocks but mostly covalent with Ga–Se blocks, as supported by electronic structure calculations. Both compounds show a nearly direct optical band gap of 1.7 eV. Their Seebeck coefficients and electrical conductivities are predicted to be similar to other oxychalcogenides, with the thermoelectric power factors being improved by n-doping. They exhibit high electrocatalytic performance for the oxygen evolution reaction, with the Pr member demonstrating superior activity, as characterized by a low overpotential of 257 mV (at a current density of 10 mA cm –2 ), a high mass activity of 70.1 A g –1, and a turnover frequency of 0.0234 s –1 in 1 M KOH electrolyte.
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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".