Crystal Structures and Chemical Bonding of Magnesium Carbide at High Pressure
Bibliographic record
Abstract
Recent studies of the magnesium carbide (Mg–C) system under pressure were motivated by the successful high-pressure and high-temperature synthesis of Mg 2 C and Mg 2 C 3 . Here, we systematically investigate the high-pressure structures and chemical bonding of the Mg 2 C, Mg 2 C 3, and MgC 2 system using the swarm optimization technique in combination with first-principles electronic structure methodology. The structural evolution with pressure of the Mg–C systems clearly shows a systematic trend with a progressive increase of electron donation from the Mg to C. To accommodate the electrons, the C valence sp orbitals rebybridized continually and adopted different modes of chemical bonding. We demonstrated that the evolution of the electronic and crystal structures can be explained from a Zintl–Klemen charge-transfer concept. Therefore, at sufficiently high pressure metallic MgC 2 and Mg 2 C transformed to semiconductors, while Mg 2 C 3 undergoes an insulator–metal transition. The present results established the richness of carbon bonding of different stoichiometries under high pressure.
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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) | 0.001 | 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 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".