Hidden Thermodynamic Ground State of Calcium Diazenide
Bibliographic record
Abstract
A new member to the family of alkaline earth diazenides, calcium diazenide (CaN 2 ), was recently synthesized by a controlled decomposition of calcium azide at high-pressure/high-temperature conditions (Schneider et al. Inorg. Chem. 2012, 51, 2366–2373). Isotypic to tetragonal calcium carbide, the synthesized CaN 2 phase adopts a tI6 structure in which Ca 2+ cations and [N 2 ] 2- anions are arranged in a distorted rocksalt structure. Using an unbiased structure searching method, we investigate the energy landscape of CaN 2 at the first principles level and suggest that the tI6 structure is a metastable form of CaN 2 . A new orthorhombic oP12 structure, formed by a distorted bcc lattice of Ca 2+ cations interpenetrated by [N 2 ] 2- anions, is predicted to be the thermodynamic ground state of CaN 2 . The energy of the oP12 structure is considerably lower than that of the synthesized phase, by ∼80 meV/CaN 2, while it is also lower than the energies of the candidate structures previously considered. The oP12 structure remains as the thermodynamic ground state of CaN 2 at high pressures up to 2.9 GPa, at where it undergoes a first-order phase transition to a higher density oP12′ structure. Above 2.9 GPa, the synthesized tI6 phase becomes the thermodynamic ground state of CaN 2 . The formation of the oP12 structure is predicted to be exothermic which suggests that this structure may be synthesized in future experiments with proper experimental conditions.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".