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AuthorSuter, J.L.
AuthorKabalan, L.
AuthorKhader, M.
AuthorCoveney, P.V.
Available date2015-12-29T12:54:35Z
Publication Date2015-11
Publication NameGeochimica et Cosmochimica Acta
ResourceScopus
Identifierhttp://dx.doi.org/10.1016/j.gca.2015.07.013
CitationSuter J.L., Kabalan L., Khader M., Coveney P.V., Ab initio molecular dynamics study of the interlayer and micropore structure of aqueous montmorillonite clays, (2015) Geochimica et Cosmochimica Acta, 169, pp. 17-29
ISSN0016-7037
URIhttp://hdl.handle.net/10576/4004
AbstractAb initio molecular dynamics simulations have been performed to gain an understanding of the interfacial microscopic structure and reactivity of fully hydrated clay edges. The models studied include both micropore and interlayer water. We identify acidic sites through dissociation mechanisms; the resulting ions can be stabilized by both micropore and interlayer water. We find clay edges possess a complex amphoteric behavior, which depends on the face under consideration and the location of isomorphic substitution. For the neutral (110) surface, we do not observe any dissociation on the timescale accessible. The edge terminating hydroxyl groups participate in a hydrogen bonded network of water molecules that spans the interlayer between periodic images of the clay framework. With isomorphic substitutions in the tetrahedral layer of the (110) clay edge, we find the adjacent exposed apical oxygen behaves as a Br?nsted base and abstracts a proton from a nearby water molecule, which in turn removes a proton from an AlOH<inf>2</inf> group. With isomorphic substitutions in the octahedral layer of the (110) clay edge the adjacent exposed apical oxygen atom does not abstract a proton from the water molecules, but increases the number of hydrogen bonded water molecules (from one to two). Acid treated clays are likely to have both sites protonated. The (010) surface does not have the same interfacial hydrogen bonding structure; it is much less stable and we observe dissociation of half the terminal SiOH groups (?Si-O-H??SiO-+H+) in our models. The resulting anions are stabilized by solvation from both micropore and interlayer water molecules. This suggests that, when fully hydrated, the (010) surface can act as a Br?nsted acid, even at neutral pH.
SponsorQatar National Research Fund (QNRF) of Qatar Foundation, National Priorities Research Program (grant number 09-26-01-048). Our work made use of the facilities of HECToR, the UK's national high-performance computing service, which is provided by UoE HPCx Ltd at the University of Edinburgh, Cray Inc and NAG Ltd, and funded by the Office of Science and Technology through EPSRC's High End Computing Programme. Access to HECToR was through grants EP/F00521/1, EP/E045111/1, EP/I017763/1 and the UK Consortium on Mesoscopic Engineering Sciences (EP/L00030X/1). We also made use of High Performance Computing facilities at University College London.
Languageen
PublisherElsevier Ltd
Subjectexperimental mineralogy
Subjectmicrostructure
Subjectmineral property
Subjectmolecular analysis
Subjectmontmorillonite
TitleAb initio molecular dynamics study of the interlayer and micropore structure of aqueous montmorillonite clays
TypeArticle
Pagination17-29
Volume Number169


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