Polymerization of Carbon Dioxide: A Chemistry View of Molecular-to-Nonmolecular Phase Transitions
Bibliographic record
Abstract
Under high pressure, simple molecular solids transform into nonmolecular (extended) solids as compression energies approach the energies of strong covalent bonds in constituent chemical species. Unlike molecular and extended phase transitions, these exhibit path dependent phases, phase boundaries, phase metastabilities, and structural distortions that lead to large uncertainties in both experimental and theoretical phase diagrams. Here we present experimental and theoretical evidence that carbon dioxide polymerizes to extended phase V at 20 GPa, indicating a substantially lower equilibrium phase boundary than previously suggested. Clearly, these results indicate extended structures are inherently more stable above 20 GPa and the presence of a strong activation barrier hindering the polymerization in the intermediate pressure region between 20 and 40 GPa. Further, the present results advocate a chemistry view of molecular to nonmolecular phase transitions governed by constraints to kinetics and local energy minima that go beyond thermodynamics and are analogous to the graphite–diamond transition.
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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 | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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 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".