@article{SternemannWilke2016,
  author    = {Sternemann, C. and Wilke, Max},
  title     = {Spectroscopy of low and intermediate Z elements at extreme conditions: in situ studies of Earth materials at pressure and temperature via X-ray Raman scattering},
  series = {High pressure research},
  volume    = {36},
  journal   = {High pressure research},
  publisher = {IOP Publ. Ltd.},
  address   = {Abingdon},
  issn      = {0895-7959},
  doi       = {10.1080/08957959.2016.1198903},
  pages     = {275 -- 292},
  year      = {2016},
  abstract  = {X-ray Raman scattering spectroscopy is an emerging method in the study of low and intermediate Z elements' core-electron excitations at extreme conditions in order to reveal information on local structure and electronic state of matter in situ. We discuss the capabilities of this method to address questions in Earth materials' science and demonstrate its sensitivity to detect changes in the oxidation state, electronic structure, coordination, and spin state. Examples are presented for the study of the oxygen K-, silicon L- and iron M-edges. We assess the application of both temperature and pressure in such investigations exploiting diamond anvil cells in combination with resistive or laser heating which is required to achieve realistic conditions of the Earth's crust, mantle, and core.},
  language  = {en}
}
@article{CerantolaWilkeKantoretal.2019,
  author    = {Cerantola, Valerio and Wilke, Max and Kantor, Innokenty and Ismailova, Leyla and Kupenko, Ilya and McCammon, Catherine and Pascarelli, Sakura and Dubrovinsky, Leonid S.},
  title     = {Experimental investigation of FeCO3 (siderite) stability in Earth's lower mantle using XANES spectroscopy},
  series = {American mineralogist : an international journal of earth and planetary materials},
  volume    = {104},
  journal   = {American mineralogist : an international journal of earth and planetary materials},
  number    = {8},
  publisher = {Mineralogical Society of America},
  address   = {Chantilly},
  issn      = {0003-004X},
  doi       = {10.2138/am-2019-6428},
  pages     = {1083 -- 1091},
  year      = {2019},
  abstract  = {We studied FeCO3 using Fe K-edge X-ray absorption near-edge structure (XANES) spectroscopy at pressures up to 54 GPa and temperatures above 2000 K. First-principles calculations of Fe at the K-edge in FeCO3 were performed to support the interpretation of the XANES spectra. The variation of iron absorption edge features with pressure and temperature in FeCO3 matches well with recently reported observations on FeCO3 at extreme conditions, and provides new insight into the stability of Fe-carbonates in Earth's mantle. Here we show that at conditions of the mid-lower mantle, ~50 GPa and ~2200 K, FeCO3 melts and partially decomposes to high-pressure Fe3O4. Carbon (diamond) and oxygen are also inferred products of the reaction. We constrained the thermodynamic phase boundary between crystalline FeCO3 and melt to be at 51(1) GPa and ~1850 K. We observe that at 54(1) GPa, temperature-induced spin crossover of Fe2+ takes place from low to high spin such that at 1735(100) K, all iron in FeCO3 is in the high-spin state. A comparison between experiment and theory provides a more detailed understanding of FeCO3 decomposition observed in X-ray absorption spectra and helps to explain spectral changes due to pressure-induced spin crossover in FeCO3 at ambient temperature.},
  language  = {en}
}