Iron is the most abundant element in the earth’s core, however, a difficulty of measuring equilibrium states at high temperatures and pressures ( > ~0.1 (MBar) and thousands of (K)), resulted in an unknown iron phase diagram at earth core condition.

Based on Granato’s interstitialcy model, we had develop a model for the free energy of the liquid that allows for reconstruction of the melting line from existing data on the solid phases and the explored melting region.

We introduce explicit free energies for the high T and P phases of iron (F.C.C and H.C.P), which reproduce published experimental phase line. We then use the derived model to fit a liquid free energy per solid phase. We show that a fit based on the F.C.C-liquid line up to 100 (GPa) and 4000 (K), allows for extrapolation of both melting line as well as various thermodynamic properties over a significantly wider range (up to 300(GPa) and 7000(K)). Using the same methodology we indicate to the possibility of phase transition between separate liquid phases, namely a transition between F.C.C-based liquid to an H.C.P-based liquid.