Comparative Analysis of the Crystal Structures and Physical Properties of the Complex Group 14 Selenides Sr<sub>8</sub>Ge<sub>4</sub>Se<sub>17</sub> and Ba<sub>8</sub>Sn<sub>4</sub>Se<sub>17</sub>
Bibliographic record
Abstract
During our group’s continued exploration of group 14 chalcogenides, we discovered two new compounds, Sr 8 Ge 4 Se 17 and Ba 8 Sn 4 Se 17 . Both compounds have an 8:4:17 stoichiometric ratio but adopt different centrosymmetric crystal structures. Sr 8 Ge 4 Se 17 crystallizes in the triclinic P 1̅ space group with a = 11.8429(18) Å, b = 12.172(3) Å, c = 13.624(3) Å, α = 114.472(5) 0, β = 97.396(5) 0, γ = 107.040(5) 0, and Z = 2. Ba 8 Sn 4 Se 17 crystallizes in the monoclinic C 2/ c space group with a = 47.286(3) Å, b = 12.6294(5) Å, c = 25.7303(15) Å, β = 104.585(5) 0, and Z = 16. The unit cell of Ba 8 Sn 4 Se 17 is approximately eight times larger than the unit cell of Sr 8 Ge 4 Se 17, which is a consequence of the differently aligned tetrahedra, resulting in a quadrupled a axis, unchanged b axis, and doubled c axis. The lattice parameters and atomic coordinates were finalized via Rietveld refinements on data collected at a high-energy synchrotron beamline. Both compounds are semiconductors with band gaps in the visible region. Sr 8 Ge 4 Se 17 and Ba 8 Sn 4 Se 17 have optical band gaps of 1.88 and 1.93 eV, respectively. Both compounds have remarkably low thermal conductivities owing to their low symmetries and large unit cells. The minimum experimental thermal conductivity values of Sr 8 Ge 4 Se 17 and Ba 8 Sn 4 Se 17 are 0.45 W m –1 K –1 at 321 K and 0.31 W m –1 K –1 at 324 K, respectively.
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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) | 0.002 | 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".