Elastic properties of Earth materials

The study of the high-pressure elastic properties of minerals is crucial to construct reliable global models of the Earth structure and dynamics, consistent both with geophysical and geochemical evidence.; By combining new high-pressure X-ray diffraction of MgO (periclase) performed in quasi-hydrostatic conditions with existing experimental data, I have determined parameters for the thermal equation of state of MgO that correctly describe the high-pressure and high-temperature data to 203 GPa and 3663 K.; I have measured the elastic tensor of CaF2 (fluorite) to 9.3 GPa and I have determined an independent density scale for this important secondary standard in moderate high-pressure X-ray diffraction studies. Comparing the Brillouin scale and the existing X-ray diffraction scale I could quantitatively evaluate 1% the accuracy of fluorite pressure scale.; I have studied the elasticity of fayalite, Fe2SiO4, to 12.1 GPa at ambient temperature. The results demonstrate that Fe-Mg substitution increases the bulk modulus of olivine and its pressure dependence; it reduces the shear modulus but has no effect on its pressure dependence. I was able to better quantify the compositional dependence of the elastic moduli of olivine, which can be responsible for seismic velocity anomalies in Fe-enriched regions of the upper mantle.; I have tested the reliability of radial X-ray diffraction as a method to determine elastic properties of minerals at high pressures by combining radial X-ray diffraction to 65 GPa and Brillouin spectroscopy of CaO to 25 GPa. I determined the elastic tensor and the high-pressure yield strength of CaO. The X-ray elastic constants are in excellent agreement with the spectroscopic ones up to 25 GPa. Discrepancies at higher pressure can be reconciled within the framework of the lattice strain theory.; I have investigated the elasticity of tetragonal crystals of lysozyme and the effect of relative humidity (to 68%) by Brillouin scattering at ambient pressure and temperature. I interpreted the results by modeling tetragonal lysozyme as a composite made up of rigid molecular units linked by mainly electrostatic and van der Waals interactions weakened by the presence of intermolecular bulk water.