We introduced experimental measurements on presses with diamond cell anvils, combined from the 1990s with in situ measurements by X-ray diffraction and other methods made possible by the installation of presses in synchrotron centers. We have described ab initio theoretical methods, which have recently enjoyed a boom thanks to the development of computer power. The various methods of measurement have recently come into agreement with a relatively high melting point temperature for iron, around 6,000 K.
Experimental and theoretical measurements also address the question of the stable crystalline phase of iron in the seed (Hcp or Bcc?), which has implications for the nature of the anisotropy, the partitioning of light elements between the seed and the outer core, which has an impact on the temperature at the ICB (depression of the order of 500 K). Part of the lecture was devoted to a discussion of the nature of the light elements in the seed and outer core and the nature of the constraints (cosmochemical, material physics) that would make it possible to specify it.
Among the unresolved questions at present is the important one of shear velocity in the seed: experimental and theoretical measurements predict higher velocities than those observed by seismology, even after various corrections (anharmonicity etc., cf. Antonangeli et al., 2010).
