Application of inelastic X-ray scattering to the measurements of acoustic wave velocities in geophysical materials at very high pressure

Reference Earth global models used by geophysicists are mostly constrained by analysing seismic waves that travel in the Earth. The interpretation of these seismological models in terms of chemical composition and temperature thus relies on the knowledge of the chemical composition, structure and elastic properties of some candidate materials relevant to geophysics. We will describe some recent advances in experimental mineral physics which yield essential information on the elastic properties of pertinent materials of Earth’s mantle and core. In particular, we show that inelastic X-ray scattering (IXS) proves to be a well suited spectroscopic technique for the study of phonon dispersion in materials under high pressure. Inelastic scattering experiments carried out on polycrystalline samples provide measurements of orientationally averaged longitudinal acoustic velocities whereas investigations on single crystals yield elastic moduli. Such a technique is thus highly interesting for mineral physicists and offers a great potential in providing essential elastic data and their pressure and/or temperature dependence on most compounds of geophysical interest.