The Earth's solid core is mostly composed of iron. However, the stable phase of iron under inner-core conditions remains uncertain. The two leading candidates are hexagonal close-packed (hcp) and body-centred cubic (bcc) crystal structures, but the dynamic and thermodynamic stability of bcc iron under inner-core conditions has recently been challenged. We demonstrate the stability of the bcc phase of iron under conditions consistent with the centre of the core using ab initio molecular dynamics simulations. We find that the bcc phase is stabilized at high temperatures by a novel diffusion mechanism that arises due to the dynamical instability of the phase at lower temperatures [1]. 

1. A. B. Belonoshko, T. Lukinov, J. Fu, J. Zhao, S. Davis, and S. I. Simak, "Stabilization of body-centred cubic iron under inner-core conditions", Nature Geoscience 10, 312 (2017).