High-pressure and high-temperature studies: structural evolution and phase transitions in minerals and their effect on intrinsic properties

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Fundamental knowledge of the stability of minerals and the arrangement of atoms in their crystal structure as they exist deep in the Earth are important for providing realistic models for Earth processes. This research program attempts to answer the questions, why do solid materials have the properties that they exhibit? How do these properties change under different pressure and temperature (P and T) conditions? How does the ordering of atoms in a structure change in response to P and T? What are the effects of order-disorder on intrinsic properties? Physical, mechanical, thermodynamic, elastic, and chemical properties are governed by the arrangement of atoms in a solid on an atomic scale. Therefore, it is necessary to determine the atomic structures of materials, including minerals, using a multi-disciplinary approach and using various in situ experimental techniques to investigate the processes that govern their stabilities and properties under non-ambient (different P and T) conditions, including composition and time, and applying the results to Mineral Physics and Earth processes. The applicant is an established synchrotron radiation researcher who has used state-of-the-art experimental techniques at National Facilities in USA and France (APS, NSLS, and ESRF) and hopes to use or establish similar techniques at the Canadian Light Source (CLS) at Saskatoon. My research program is based heavily on physical chemistry and diffraction physics using laboratory techniques and synthesis, X-ray structure analyses, spectroscopy, electron microscopy, element analyses, and thermal analyses, in addition to active research at National Synchrotron and Neutron Facilities. Selected minerals will be examined in situ under different P and T conditions. The resulting information will provide insight into the mechanisms by which minerals are formed, and provide a quantitative understanding of Earth processes. With varying P and T, minerals may undergo changes in cation/anion order-disorder. These order-disorder processes may have significant effect on the velocities of sound waves in the Earth. Therefore, order-disorder effects need to be taken into account when geophysical models are proposed for the Earth.