Interactions between Structure H Hydrate Formers and Water Molecules
Bibliographic record
Abstract
Studies on methane storage in hexagonal structure H (sH) hydrates reveal that hydrate stability conditions, formation rates, and cage occupancies differ for the three large molecule guest substances (LMGSs) studied: tert -butyl methyl ether (TBME), neo-hexane (NH), and methyl-cyclohexane (MCH). In this work, the structures of aqueous solutions with the LMGS are examined with molecular dynamics to gain insights into the interactions between water and LMGS. Water molecules form solvation cavities that follow the contours of the LMGS molecules and have diameters between 4 and 7 Å. The cavity size increases from TBME < NH < MCH, and the nearest water molecules to the LMGS have a local density that is higher by a factor of 2 than that of the bulk water phase. Water molecules interact strongly with the ether oxygen of TBME but not with other atoms in the LMGS molecules. This strong attraction gives TBME a greater solubility in water and better wetting on ice than NH or MCH. Moreover, TBME also has a larger diffusivity than NH in water. The greater contact between TBME and the host water molecules may cause the faster rate of initial hydrate growth from solid ice particles (fixed bed) or liquid water with mixing for this guest species. However, the strong attraction of the TBME molecule with water may also slow down the subsequent crystal growth and may perhaps limit the occupancy of the other guests (methane) in the sH clathrate. The volume change due to solvation is negative for all three LMGSs. This suggests a more compact hydrogen bond network in the hydration shell that may facilitate the formation of clathrates when a hydrate seed is available and when mass and heat transfer resistances are negligible. For example, this may occur during hydrate formation from a fixed ice bed with temperature ramping. Hence, the clathrate growth with hydrophobic guests (NH and MCH) proceeds rapidly toward completion as the temperature is increased above the ice melting point. On the other hand, the formation of hydrate cages for the TBME system is disrupted because of the strong water−solute interactions. Consequently, hydrate formation from ice with thermal ramping with TBME is slower.
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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) | 0.002 | 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".