The behavior of minerals at ultrahigh pressures and temperatures controls the inner workings of the Earth. The goals of this proposed work are to measure phase stability, density, compressibility, and thermoelastic properties of what is likely the predominant deep-mantle suite of minerals-MgSiO3-at the relevant pressure and temperature conditions of the deep Earth. The ability of in-situ high pressure measurements in the laser heated diamond cell to constrain these properties has been severly limited by the behavior of the sample inside the diamond cell sample chamber. The sample geometry-which often consists of a marker material embedded in the study material matrix-will generate errors and uncertainties in measurement. However, the accuracy and precision of measurements can be significantly improved when the sample geometry is controlled. These improvements are a feature of our proposed work. The specific tasks include: 1) Sol-gel processing of samples consisting of alternating layers of MgSiO3 and metal marker starting materials; 2) Studies of the stress environment of the sample chamber, especially during laser heating.; 3) X-ray diffraction measurements at high pressures for density and compressibility measurements; 4) X-ray diffraction coupled with laser heating to determine phase stability and constrain thermoelastic properties of MgSiO3; and 5) Finite element modeling of the stress state inside the sample chamber. The results have important implications on both technical and scientific fronts. Technically, this research will advance our ability to intelligently design samples for geophysical measurements. Scientifically, the results will contribute to our understanding of how the deepest mantle helps govern the current state and evolution of the whole Earth.
