Strong correlation between ionic bonding strength and superconductivity in compressed hydrides
Bibliographic record
Abstract
Understanding the superconductivity in relation to chemical bonding is essential for the development of superconductors. We propose that pressure-reduced ionic bonding strength is beneficial for improving superconductivity in hydrides (negative correlation between bonding strength and critical temperature). We model ionic hydrides using a prototypical ionic lattice (CsCl-type) with simple-valence metal Li/Rb and hydrogen and control the bonding strength via external pressure. First-principles calculations reveal that the ionic bonding strength in LiH increases with pressure while its critical temperature (${T}_{\mathrm{c}}$) simultaneously decreases. A higher ${T}_{\mathrm{c}}$ at lower pressures is attributed to stronger electron-phonon coupling (EPC) induced by weaker ionic bonds and significant EPC contributions from mid-frequency phonons. RbH's pressure dependences of bonding strength and ${T}_{\mathrm{c}}$ are the reverse of those of LiH, and the EPC primarily results from high-frequency phonons. The distinct interorbital electron transition mechanism and amounts of charge transfer are responsible for the opposite trend of changes in bonding strength and superconductivity in LiH and RbH. The proposed correlation is further validated by the other six ionic hydrides. Substantial ${T}_{\mathrm{c}}$ change (e.g., 126.2 K at 100 GPa and 5.7 K at 300 GPa in LiH) in response to bonding strength variation reveals a key factor for designing new superconductors.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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 teacher head, 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".