Vibrational spectroscopy and the structure of solids: The example \nof carbonate minerals
Notice bibliographique
Résumé
Studying material structure on the atomic scale in solids can give clues as to how that material was \nformed, aged, or used. Atoms in solids are constantly in motion. A material’s specific composition \nand crystal arrangement results in a unique profile of atomic vibrations. These vibrations, or modes, \ncan be grouped into two main types; internal modes are higher energy vibrations related to atomic \nmotion of single atoms or moieties within the unit cell, whereas external modes are lower in energy \nand correspond to the collective movement of multiple coordinated atoms or moieties. Past investigations \nfocused on the vibrations of solids have explored the effect of crystalline ordering on internal \nmodes both experimentally and computationally. In this thesis, I explore the viability of established \nexperimental and computational methods to examine the influence of structural differences on the \nthe external mode vibrations using calcium carbonate as a case study material. The experimental \nprojects focus on infrared spectroscopy. This tool is sensitive enough to observe subtle differences in \nthe internal modes that are linked to structural differences but has yet to be explored for the external \nmodes. \nWe study calcium carbonate systems using infrared spectroscopic methods to understand the impact \nof structure on vibrational properties. Our initial goal was to correlate novel external mode vibration \ndata trends with the established understanding of internal mode changes and atomic structure \ndata. We found that the broadness of the external modes makes extracting structural information using \nthe previous analysis protocols impractical. The results highlight potential pitfalls for researchers \nwho are new to these spectroscopic techniques. We preach caution when attempting to interpret \nenergy shifts of external modes as structural differences amongst samples without correlating with \nadditional experimental methods. \nFurther experiments focused on photoacoustic infrared spectroscopy, a specialized version of the \ntechnique. Previous works have highlighted but failed to explain how this specialized setup can \nenhance the detection of weak internal modes. We sought to determine the mechanism for this documented \nphenomenon. While we could not identify the cause of the enhancement, our experiments \nand analysis showed that it is intrinsic to the photoacoustic method and eliminated detector saturation, \noften thought to be the cause, as the root mechanism. \nii \nFinally, I used computational molecular dynamics methods to simulate calcium carbonate vibrations. \nUsing previously published parameters, I was able to generate a vibrational density of states \n(VDOS) for the calcium carbonate polymorph aragonite. This work is valuable as alternative computational \nmethods to simulate the external vibrations of calcium carbonates are computationally \nexpensive. The computed VDOS of aragonite shows a reasonable level of qualitative agreement with \nexperimental measurements. This work serves as a proof-of-concept and starting point to observe \ndisorder’s effects on the calculated vibrational density of states.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,001 | 0,002 |
| Études des sciences et des technologies | 0,002 | 0,002 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,002 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».