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CLAY MINERALS AND THEIR GALLERY GUESTS: AN AB INITIO INVESTIGATION INTO THEIR INTERACTIONS.






Dawn L. Geatches

A Thesis presented for the degree of
[1mm]Doctor of Philosophy



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Supervised by Prof. S. J. Clark$ ^{a}$ ,
co-supervised by Dr. H. C. Greenwell$ ^{b}$
[-3mm]Departments of Physics$ ^{a}$ and Earth Sciences$ ^{b}$
[-3mm]University of Durham
[-3mm]England
[1mm]January 2011

Clay Minerals and their Gallery Guests: an ab initio investigation into their interactions.




Dawn L. Geatches


Submitted for the degree of Doctor of Philosophy
January 2011




Abstract

Clay minerals are ubiquitous and readily accessible in the natural environment and consequently have become an essential ingredient in the development of Western Society. Their structural properties are responsible for many of their uses, their layered-leaf composition enables the absorption of water and other solutes, for example. In this thesis, the focus of interest lies primarily in the chemical properties of the clay minerals, which is due to the large surface areas of varying atomistic environments comprising the mineral layers. Clay minerals offer a challenge to the electronic structure modeller as their atomistic composition is non-exact, consequently a number of constraints are automatically applied during the modelling process, the first being the choice of composition of the model. There are currently few examples of density functional theory studies using planewaves and the pseudopotential approximation, and the available experimental data is not necessarily directly applicable to theoretical data due in part, to the inexactness of the clay mineral composition. Consequently, in the studies presented in this thesis, as much time has been spent in considering the modelling methods as on the results obtained and the implication of these in the modelling environment chosen.

This thesis records investigations into the decarboxylation of a fatty acid into an alkane and CO$ _{2}$ with the modelling of a catalytic environment of an aluminium-bearing clay mineral; the identification of a transition state of this reaction pathway using lattice dynamics and finally, the mechanism of reduction within iron-bearing clay minerals.




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Stewart Clark 2012-08-09