Electronic Structures and Properties of RE<sub>12</sub>Ga<sub>4</sub>Sb<sub>23</sub> (RE = La−Nd, Sm) and Superconducting La<sub>13</sub>Ga<sub>8</sub>Sb<sub>21</sub>
Bibliographic record
Abstract
The bonding in the related structures of La 12 Ga 4 Sb 23 and La 13 Ga 8 Sb 21 has been analyzed following a retrotheoretical approach, with the use of extended Hückel calculations. Once the La 3+ cations have been removed, the [Ga 4 Sb 23 ] 36 - and [Ga 8 Sb 21 ] 39 - metalloid networks can be decomposed into two noninteracting substructures: [(GaSb 3 ) 2 (Ga 2 Sb 17 )] 36 - (in La 12 Ga 4 Sb 23 ) and [(GaSb 3 ) 2 (Ga 6 Sb 15 )] 39 - (in La 13 Ga 8 Sb 21 ). Trigonal planar GaSb 3 units are stacked in a one-dimensional array in La 12 Ga 4 Sb 23 . A pairing distortion results in slight pyramidalization of the GaSb 3 units and weak interunit Ga−Ga bonding in the [GaSb 3 ] substructure of La 13 Ga 8 Sb 21 . The one-dimensional [GaSb 3 ] stacks are enclosed by networks of Ga-linked square Sb ribbons, [Ga 2 Sb 17 ] and [Ga 6 Sb 15 ]. These networks can be related to a prototypical square sheet of Sb atoms and the oxidation states assigned accordingly. The puckering of the unusual Ga 6 ring that occurs in the [Ga 6 Sb 15 ] network of La 13 Ga 8 Sb 21 is attributed to the stabilization of bands derived from the ring π system by strengthened Ga−Sb bonding to half of the adjacent Sb atoms. When the La 12 Ga 4 Sb 23 and La 13 Ga 8 Sb 21 structures are reassembled, the Fermi levels fall in a region of moderate density of states, consistent with metallic behavior. Resistivity measurements for the complete RE 12 Ga 4 Sb 23 (RE = La−Nd, Sm) series confirm that all are metallic. La 13 Ga 8 Sb 21 exhibits metallic behavior at high temperatures, but undergoes a metal−superconductor transition at T c = 2.4 K. Magnetic measurements corroborate this result.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.002 | 0.002 |
| Meta-epidemiology (broad) | 0.003 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.000 | 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; both teacher heads agree on what is shown here.
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".