Compressibility and Structure of Silicate Melts at High Pressure

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This project involves a laboratory investigation of the elastic properties and structure of hydrated and anhydrous alkali silicate melts under in-situ high pressure and temperature conditions in the externally heated diamond anvil cell (DAC) by Brillouin light scattering (BLS) technique. This technique allows measurements of both VP and nVP (where VP is compressional velocity and n is refractive index) simultaneously by a "modified" Brillouin platelet scattering geometry in diamond anvil cell,In conjunction with the Brillouin measurements, the investigators are also carrying out Raman scattering studies in order to correlate the measured elastic properties with the structure of the melt. These studies are conducted on hydrated and anhydrous alkali silicates with a range of cation sizes and different degrees of melt polymerization. As such, these data are enabling to constrain the structural systematics of melt elasticity at pressure, providing insight into the role of pressure-induced changes as well as water inmelt structure in altering melt compressibility. One major goal is to compare the possible structural and elastic changes occurring in both silicic (silica-rich) and mafic (iron-rich) melts under compression. The other major scientific goal is to carry out the in situ high P-T DAC experiments, involving both Brillouin and synchrotron x-ray microtomography simultaneously, at the GSECARS beam line of the Advanced Photon Source, Argonne National Laboratory, for determining the elastic properties (compressibility and densification) of silicate melts more precisely,Pursuing technically challenging and intellectually stimulating questions are expected to sufficiently sharpen scientific acumen of students and post-doctoral researchers involved, so they will become the next generation of scientists. The success of this study has potential value in future high P-T light scattering experiments in the DAC, and is expected to impact Earth and materials sciences and engineering, providing useful implications for society, industry, and defense needs.