Theoretical investigation of the electronic structure and transport properties of Na<sub>1+<i>x</i></sub>Co<sub>2</sub>O<sub>4</sub>
Bibliographic record
Abstract
The validity of a simple band description for explaining the unexpectedly large thermopower in Na 1+ x Co 2 O 4 was investigated. Non-spin-polarized and spin-polarized electronic structures of layered cobalt oxides Na 1+ x Co 2 O 4 are studied by means of first-principles density functional theory calculations. The fractional occupancy of Na is described via two approaches—the virtual crystal approximation and the rigid band model. We also found that the band structure of the valence band is very sensitive to the geometry of the CoO 6 ‘octahedron’, and cannot be described by a simple crystal field model. The Seebeck coefficients are calculated from the standard kinetic theory. The calculated thermopower demonstrates the importance of a high density of states close to the Fermi level. The calculated Seebeck coefficient based on the paramagnetic band structure is apparently in good agreement with experimental observation although it has been suggested that spin entropy may dominate the thermopower. However, the calculation failed to account for the observed negative in-plane Hall coefficient.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".