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Molecular solids at high pressure

Quesada Cabrera, R.; (2009) Molecular solids at high pressure. Doctoral thesis, UCL (University College London).

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Abstract

High pressure science has extended its applications beyond its classic domain of physics and geophysics. Diamond anvil cell techniques have been adapted to the study on chemical transformations at high pressure and pressure-modified reaction kinetics, contributing to a better understanding of reaction processes and new preparative strategies and opening unexplored chemical pathways for new materials. In this thesis, we aim to present examples of the contribution of the diamond anvil cell to high pressure science, as well as to explore potential applications for this revolutionary perturbation tool. We first introduce a study on sodium silicide (NaSi), a Zintl phase, a potential compound for polymerization at high pressure. This system is an interesting model that illustrates some of the common processes observed in high pressure research. The investigation on the behaviour of sodium orthonitrate (Na3NO4) at high pressure aimed to analyse possible routes towards the synthesis of as yet unknown orthocarbonates and maybe discover compounds with an ever higher coordination for nitrogen or a NO4-containing three-dimensional network. Recently synthesised polyoxometalate (POM) clusters have shown interesting thermochromic properties, which has been related to a redox reaction occurring within the metal-oxygen cage. At high temperature, it has been proposed that the SO3 heteroanion groups contained in the cluster transform to SO4 by the introduction of bridging oxygen from the cage. An oxygen rearrangement would reduce up to four metal atoms, inducing the colour change. We aimed to investigate here whether a similar electron localization process is possible upon compression of these systems. Finally, we develop pioneering high-pressure DAC experiments on amyloid fibrils, using synchrotron X-ray diffraction. Our approach allows us to estimate the Young’s modulus of these biological macromolecular materials and discuss their low compressibility for applications in nanotechnology.

Type:Thesis (Doctoral)
Title:Molecular solids at high pressure
Language:English
Additional information:Authorisation for digitisation not received
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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