Electronic structure of iron and models of the Earth's core

The possibility that iron might undergo a transition to the 3d8 state at core pressures is investigated. A detailed calculation of the electronic band structure of iron indicates that the transition occurs at approximately fourfold compression. At core pressures, the band structure is essentially similar to that at STP conditions. Thus, it appears that the only proposed alternative to freezing as the mechanism for the formation of the inner core from the outer core has been disqualified. In addition, a quantum mechanical calculation of the density and bulk‐modulus of iron gives values which are in excellent agreement with the latest inner core models. On the other hand, the density of the outer core is significantly lower than that of pure iron. This lends strong support to those theories which postulate an essentially pure iron solid inner core, and significant amounts of impurities in the outer core.