Structure, Composition, and Thermal Expansion of CO<sub>2</sub> Hydrate from Single Crystal X-ray Diffraction Measurements
Bibliographic record
Abstract
The structure and composition of CO 2 hydrate were determined from single-crystal X-ray diffraction data at 173 K for a crystal grown over heavy water and liquid CO 2 . Superior diffraction data allowed the derivation of a structural model of unprecedented quality for the hydrate, giving the location of the disordered CO 2 molecules in the two cages. In the large cage, the guests are shown to be off-center, with a bimodal distribution of out-of-plane orientations for the long axis of the molecule (173 K). Also, the absolute cage occupancies were determined from the structural model, thus allowing a reliable and direct evaluation of the hydrate composition for this crystal, CO 2 ·6.20(15) D 2 O. The temperature dependence of the lattice parameters for the single crystal was measured between 123 and 223 K and found to be in good agreement with recent neutron powder diffraction results, and data from all sources were fit to a single polynomial function. The hydrate composition and density are discussed in terms of the information needed for the deep-sea sequestration of CO 2 . The guest disorder and dynamics are discussed in terms of the model derived from earlier NMR data.
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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 | 0.001 |
| 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".