Viscosity of the Inner Core

The Earth Core is mostly iron. The inner part of it is a solid inner core (IC). The attempts to explain the enigmatic properties of the IC by the stability of the hexagonal close-packed (hcp) phase were not very successful. Recently, it was demonstrated by first-principles molecular dynamics (FPMD) method that the stable phase of iron under pressure (330-360 GPa) and temperature (5500-8000 K) of the IC is the body-centered cubic (bcc) phase. This phase was actually already observed in experiments but some of the shockwave data was likely misinterpreted. There is also a very recent diamond anvil cell experiment that confirms the stability of the bcc phase. One of the enigmatic properties of the IC is high attenuation of seismic waves. The attenuation of the hcp phase is quite low. We computed, using FPMD, that the bcc phase possess the viscosity that explains the high attenuation in the IC. The explanation is in the unique feature of the bcc phase - iron atoms diffuse preserving the bcc lattice. This feature of the bcc phase provides a strong evidence in favor of the bcc stability in the IC.