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Center for Nonlinear Studies |
Metakaolin is a disordered layered aluminosilicate produced via calcination of kaolin clay. It has a variety of uses including as a cement additive, a geopolymer precursor and as an intermediate phase in ceramic processing. Given the extent to which metakaolin is used in industry and research, it is surprising not more effort has been placed on resolving the structure of this material. However, this is understandable as metakaolin is structurally disordered and does not provide distinct Bragg reflections and is therefore difficult to characterize using standard crystallography techniques. Hence, here we outline the methodology used to characterize a disordered material, which includes first principles modelling, synchrotron X-ray diffraction and neutron total scattering. This methodology commences with modelling of the crystalline parent material, kaolinite, in order to validate the computational approach selected. Then a novel synergy between total scattering and density functional modelling is exploited to obtain an atomic representation of the local structure of metakaolin. This structure not only “fits” with experimental results, it is energetically favorable. Hence, this methodology provides the first accurate and detailed atomic description of the local structure of this highly disordered material.
Host: Lenka Zdeborova, T-4/CNLS