Thermoelastic properties of post-perovskite phase MgSiO3 determined experimentally at core–mantle boundary P–T conditions

We have performed in-situ X-ray diffraction measurements on MgSiO3 up to 144.5 GPa and 2535 K to obtain a precise experimental determination of the elastic properties of the post-perovskite polymorph of MgSiO3 at high pressure and temperature. The complete dataset is comprised of 24 data points at ambient temperature and an equal number at high temperature. Fitted physical properties are the room temperature bulk modulus, the Grüneisen parameter with its volume dependency, the thermal expansion with its temperature dependency, and the linear incompressibilities as well as thermal expansions and their temperature dependency on each axis. Elastic anisotropy is observed, the structure being much more compressible along the b axis, and less compressible along the c axis, in agreement with theoretical calculations. We also demonstrate with the present study that experiments can provide precise information on the elasticity of complex materials at extreme pressure and temperature conditions.