A combined experimental and theoretical evaluation of the structure of hydrated microporous aluminophosphate AlPO4-18.
J Phys Chem B
; 109(48): 22939-46, 2005 Dec 08.
Article
de En
| MEDLINE
| ID: mdl-16853989
ABSTRACT
Water adsorption in the microporous aluminophosphate AlPO4-18 is studied by a combination of solid-state NMR, X-ray diffraction, and density functional theory calculations. The change of the framework structure upon hydration is moderate, and NMR gives local information on the environment of Al and P atoms. The structural distribution of water molecules in the channels has been explored by a combination of first-principle molecular dynamics simulations and of static geometry optimizations. Two starting points have been considered for the calculations. If the structure of the dehydrated aluminophosphate is used, the simulation result is not satisfactory with an incomplete hydration and no agreement with NMR results. Starting from a partial refinement of the aluminophosphate framework for the hydrated system, a structure with six tetrahedral and six octahedral Al atoms in the unit cell is obtained, involving twelve water molecules coordinated to Al atoms and twelve others in the channels, and in good agreement with experimental data.
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Collection:
01-internacional
Base de données:
MEDLINE
Langue:
En
Journal:
J Phys Chem B
Sujet du journal:
QUIMICA
Année:
2005
Type de document:
Article
Pays d'affiliation:
France