Structural Investigation of Silicalite-I Loaded with <i>n</i>-Hexane by X-ray Diffraction, <sup>29</sup>Si MAS NMR, and Molecular Modeling
Bibliographic record
Abstract
The room temperature (298 K) structure of zeolite Silicalite-I loaded with approximately eight n -hexane molecules per unit cell was solved from twinned single-crystal X-ray diffraction (XRD) data in the monoclinic space group P 12 1 / n 1 with a = 19.8247(2) Å, b = 20.1292(2) Å, c = 13. 4510(2) Å, and β = 90.29(8)°. At this temperature, the guest molecules are dynamically disordered and distributed throughout the entire channel system. The structure determined from a Rietveld refinement of room-temperature powder XRD data, which is not affected by the twinning, confirmed this. A twinned crystal refinement was also carried out for data collected at 180 K ( P 12 1 / n 1, a = 19.9310(2) Å, b = 20.1730(3) Å, c = 13.4191(3) Å, β = 90.20(5)°). At 180 K, the sorption sites of the n -hexane molecules are well-defined within the channel system, being located only in the straight and sinusoidal channels, leaving the intersections unoccupied. This ordering is commensurate with the framework structure of Silicalite-I. 29 Si HPDEC MAS NMR shows that the loading of n -hexane induces a phase transition to an orthorhombic space group (most likely Pnma ) only above 340 K. Force field simulations confirm that the absorption of n -hexane molecules occurs only inside the straight and sinusoidal channels and leads to an energetically minimized host−guest structure. By optimizing the van der Waals interactions between the n -hexane molecules and the silica host framework, the nonbonding energy is minimized, leading to a general minimization of the total potential energy, and the energetically most favorable structure is obtained.
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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) | 0.001 | 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 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".