The equations of state of several constituents of the lower mantle and core will be determined at high pressures and temperatures. The compounds to be studied include (Fe,Ni) alloy, the (Mg,Fe)O series, (Mg,Fe)SiO3-perovskite, Fe3C, and FeS. Unit cell volumes and other crystallographic information are to be obtained using synchrotron x-ray diffraction while the samples are compressed and laser-heated in a diamond anvil cell. Subsolidus phase transitions will be detected and identified during the course of the equation of state measurements. Internal standards will be used for pressure calibration. The experimental methodology for these experiments has been proven successful at the Advanced Photon Source, Argonne National Laboratory. The data to be collected are critical not only to understand the seismological data, which show variations in density and elasticity within the Earth, but also for developing models of chemical evolution of the Earth. Results from the proposed study will be disseminated primarily through publication in the scientific literature, by participation at scientific conferences, and when warranted, through wider-reaching news outlets. Additional benefits of the proposed research include the continued development and refinement of experimental high-pressure, high-temperature techniques; continued exposure of university researchers, including student participants, to the facilities and talent at government-funded multi-user sites; and the training of students in the wide range of experimental techniques and scientific protocols associated with performing the proposed work.
