Water solubility in calcium aluminosilicate glasses investigated by first principles techniques Auteur(s): Bouyer F., Geneste G., Ispas S., Kob W., Ganster Patrick (Article) Publié: Journal Of Solid State Chemistry, vol. 183 p.2786 (2010) Texte intégral en Openaccess : Ref HAL: hal-00547893_v1 DOI: 10.1016/j.jssc.2010.08.031 WoS: 000285431100007 Exporter : BibTex | endNote 28 Citations Résumé: First-principles techniques have been employed to study the reactivity of water into a calcium aluminosilicate glass. In addition to the well known hydrolysis reactions Si-O-Si+h2O->Si-OH + Si-OH and Si-O-Al+h2O-> Si-OH+Al-OH, a peculiar mechanism is found, leading to the formation of an AlO3–H2O entity and the breaking of Al–O–Si bond. In the glass bulk,most of the hydrolysis reactions are endothermic. Only a few regular sites are found reactive (i.e. in association with an exothermic reaction), and in that case, the hydrolysis reaction leads to a decrease of the local disorder in the amorphous vitreous network. Afterwards, we suggest that ionic charge compensators transform into network modifiers when hydrolysis occurs, according to a global process firstly suggested by Burnham in 1975. Our theoretical computations provide a more general model of the first hydrolysis steps that could help to understand experimental data and water speciation in glasses. |