Electronic structure of Fe/Mg carbonates at conditions of the Earth's lower mantle: Implications for the formation of tetrahedrally coordinated carbon

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In this project we would like to study and describe the electronic structure of Fe in high-pressure, high-temperature tetra-carbonate phases by in situ studies of these compounds exploiting K-beta and Valence-to-Core x-ray emission spectroscopy, complemented by X-ray Raman scattering measurements. We will focus on the spin and valence state of iron, the co-existence of iron in high- and low spin-state and the influence of the ligands on the electronic structure. Furthermore, relations to the structural properties of Ca or Mg will be investigated. By combination of Valence-to-Core emission spectroscopy and X-ray Raman scattering with results from x-ray diffraction and Mössbauer spectroscopy we will constrain possible reaction paths that lead into formation of tetra-carbonate phases and assess implications for carbonates in the Earth's lower mantle.