9710003 Stixrude The PIs will address two major geological questions using a combination of high-pressure experiments (both multi-anvil devices and laser-heated diamond cells) and first-principles quantum-mechanical calculations: 1) How does the redox state affect the relative stability of the major constituents of the mantle and core? and 2) How does the redox state effect the partitioning of geophysically and geochemically important elements among major mantle and core phases? Their objective is to develop new avenues of research regarding the Earth's redox state, ranging from the practical to the fundamental: for example, from developing means of characterizing and controlling redox state in experiments at ultrahigh pressures (P) and temperatures (T), to understanding the meaning of a component's fugacity at P-T conditions far above the critical point. Multi- institutional collaboration will be an important aspect of this research both because of the diversity of state-of-the-art experimental and theoretical methods to be employed (no one or two groups have sufficient expertise), and because this will allow significant cross-checks of the results between different laboratories, between different experimental methods, and between theory and experiment. ***
