Simple Binary Molecular Mixtures at High Density: the Methane-Nitrogen System
Bibliographic record
Abstract
Mixing different molecular species at high density may yield weakly bound compounds or van der Waals solids. These novel solids are stabilized by the application of high pressure and differ in physical properties from solids formed by pure molecular species at comparable thermodynamic conditions. In this contribution, we address the importance in studying the miscibility in dense molecular mixtures and present results of the formation of binary methane-nitrogen compounds at low temperature and high pressure. Methane and nitrogen, with similar potentials and molecular sizes, are expected to be partly miscible in the condensed state. Indeed, binary van der Waals solid phases of methane and nitrogen do occur with the application of pressure. Using single crystal and powder X-ray diffraction with synchrotron radiation, and vibrational spectroscopy, the pressure-concentration phase diagram for this system has been explored from 1 to 16 GPa at room temperature. The existence of novel van der Waals solid phases for samples with concentrations above 10% (methane per volume) is demonstrated. For example, at 7.6 GPa and at room temperature, whereas pure nitrogen and methane exist in a cubic (Pm3n) and in a rhombohedral structure (R-3/m), respectively, our study indicates that a methane-nitrogen sample with ~ 40% methane by volume exhibits, under the same conditions, a novel phase with a tetragonal symmetry with lattice parameters a ~ 11.9 Å and c ~ 6.2 Å. Other novel structures in methane-nitrogen samples with different concentrations under varying pressure conditions have also been observed and will be discussed.
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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 | 0.001 |
| Open science | 0.000 | 0.001 |
| 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 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".