The Counterintuitive Relationship between Orbital Energy, Orbital Overlap, and Bond Covalency in CeF<sub>6</sub><sup>2–</sup> and CeCl<sub>6</sub><sup>2–</sup>
Bibliographic record
Abstract
High Resolution Image Download MS PowerPoint Slide The 4f orbitals of Ce(IV) have shown appreciably enhanced covalent mixing with ligand orbitals relative to those of Ce(III). Here, X-ray spectroscopy, magnetic susceptibility measurements, and theoretical methods are used to investigate 4f covalency in CeF 6 2– and CeCl 6 2– . These techniques show covalent mixing between Ce 4f and F 2p orbitals to be about 25% less than mixing between Ce 4f and Cl 3p orbitals, placing CeF 6 2– among the most ionic Ce(IV) compounds to-date. However, ligand field analysis using the experimental data shows significantly higher 4f orbital overlap with the F 2p orbitals compared to the Cl 3p. This result is counterintuitive since the Ce–F bonds display less 4f covalency despite their higher orbital overlap, and greater overlap is traditionally associated with enhanced bond covalency. The weaker covalency is attributed to the large energy gap between Ce 4f and F 2p orbitals strongly counteracting the higher orbital overlap. These results highlight that only a concerted consideration of both atomic orbital overlap and energy matching in f-element systems leads to an accurate picture of their bonding.
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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) | 0.003 | 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".