Structures and Densities of Silicate Liquids Under High Pressure

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Intellectual Merit. This proposal requests funds to support experimental studies of (1) structures of silicate liquids at high pressures, and (2) the pressure-volume-temperature (P-V-T) relations of silicate and magmatic liquids using new synchrotron x-ray diffraction and absorption methods. An x-ray scattering technique will be utilized to determine structures of liquid materials in diamond anvil cells (DAC) under a wide range of pressures up to the core mantle boundary. A newly developed x-ray absorption method will be used to measure densities of silicate liquids at high pressure-temperature conditions. To reach the required high temperatures for melting refractory silicates, a double sided laser heated DAC technique and a recently developed internally heated DAC technique are used in combination with synchrotron x-ray beams to analyze the liquid structures. An externally heated DAC and the Paris-Edinburgh cell will be used for liquid density measurements. These experiments will provide structures and densities of silicate glasses, germanate and silicate liquids, and magmatic liquids at high pressures and high temperatures. Particular effort will be put on the local structural change, including the change in coordination number, in liquids with increasing pressures. The compression behavior of both tetrahedral liquids and octahedral liquids will be determined in their stability fields. These results will provide crucial data on liquid-crystal density inversions and set constraints on differentiation and dynamic models in plausible magma oceans in planetary history. The proposed research will also provide experimental evidence for understanding the possible presence of melts in the low and ultra-low velocity zones at the bottom regions of the Earth's upper mantle and the lower mantle.Broader Impacts. This proposal supports a post-doctoral associate who will play a major role in carrying out the research activities. The PI of this proposal is a beamline scientist, with the opportunity of working with a large number of graduate students, post-doctoral scientists, and senior scientists from all over the world. The experience and technical solutions from the proposed challenging experiments are useful for outside users in performing their own. The results of the proposed research will be reported in various meetings and published in scientific journals.