A theoretical and spectroscopic study of γ-crystalline and amorphous indometacin
Bibliographic record
Abstract
Amorphous materials are prevalent in the pharmaceutical setting. Whether they are a help or hindrance, their physico-chemical characteristics must be investigated. However, the amorphous form remains a challenge to characterise with many of its properties poorly understood. In this study, gamma-crystalline and amorphous indometacin are investigated using vibrational spectroscopy and quantum chemical calculations. The structure of the single indometacin molecule and the dimer in the gamma-form were optimised using density functional theory calculations. The optimised structures were similar to the conformations in the crystal form, suggesting that conformation of the molecules in the crystal may be close to the average molecular structure in less-ordered states. Infrared and Raman spectra were calculated from the optimised structures. Many modes in the calculated spectra could be matched with the experimental spectra of the gamma-crystalline and amorphous forms, and a description of the matched modes has been provided. By analysis of the theoretical vibrational modes it was confirmed that the amorphous form of indometacin produced by quench cooling the melt consists predominantly of dimers, similar in structure to in the gamma-crystalline form. In addition, differences in intermolecular bonding between the two forms were identified. Quantum mechanical calculations allow improved understanding of amorphous materials and their vibrational spectra.
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".