Physical properties of gamma alumina surface hydroxyls revisited through a large scale periodic quantum-chemistry approach
| Autor: | Pierre Cenedese, Pierre Dubot, Anthony Dyan |
|---|---|
| Přispěvatelé: | Institut de Chimie et des Matériaux Paris-Est (ICMPE), Institut de Chimie du CNRS (INC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS) |
| Rok vydání: | 2006 |
| Předmět: |
Surface (mathematics)
[PHYS]Physics [physics] Scale (ratio) 010405 organic chemistry Chemistry Empirical modelling Cationic polymerization 02 engineering and technology Electronic structure 021001 nanoscience & nanotechnology 01 natural sciences Quantum chemistry 0104 chemical sciences Surfaces Coatings and Films Adsorption Chemical physics Computational chemistry Materials Chemistry Ideal (ring theory) Physical and Theoretical Chemistry 0210 nano-technology ComputingMilieux_MISCELLANEOUS |
| Zdroj: | Journal of Physical Chemistry B Journal of Physical Chemistry B, American Chemical Society, 2006, 110 (20), pp.10041-10050. ⟨10.1021/jp056825i⟩ |
| ISSN: | 1520-6106 1520-5207 |
| DOI: | 10.1021/jp056825i⟩ |
| Popis: | We have studied surface hydroxyls adsorbed onto (001), (011), and (111) gamma alumina surfaces using a quantum-chemistry approach in order to compare with empirical models proposed in the literature. Local electronic structures and geometries in the low OH coverage limit have been evaluated for both ideal and relaxed surfaces with the help of a large scale periodic quantum-chemical code. Hydroxyl groups are adsorbed onto surfaces, and a study of their local electronic structure, vibrational frequencies, charges, and adsorption energies is performed and analyzed as a function of their adsorption site geometry. Our results show that, even on ideal (nonrelaxed) surfaces, OH local environments are more complicated than those stated by empirical models and strongly influence the hydroxyl stretching vibrational mode. Large scale simulation shows that disorder takes place even at 0 K, and the analysis of the vibrational frequencies leads to a revision of Knözinger's empirical model. Cationic vacancies in the first surface layers have also been taken into account; they have a significant influence on the surface atomic and electronic structures, modifying the physical properties of adsorbed OH entities. This work emphasizes the necessity to perform an electronic structure calculation to better understand adsorbed OH properties on gamma alumina surfaces and reveals the difficulty to make a one-to-one correspondence between OH stretching frequencies and their other physical properties. Finally, we show that these results agree with some available experimental studies. |
| Databáze: | OpenAIRE |
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