High-pressure melting of iron: new experiments and calculations

The melting curve of ε-iron in the pressure range of 100 GPa to 300 GPa has been derived by computing Gibbs free energies at high pressures and high temperatures from equation of states (EOS) of the α-, ε- and liquid phases. Our calculations indicate that the melting curve of iron is very sensitive to the EOS of both the solid (ε) and melt phases. Optimal EOS parameters for ε-iron are presented as well as new data for sound velocities in γ- and liquid phases. The latter provides a value for the Gruneisen parameter for liquid iron of 2.55 at 9.7 Mg m^(-3) at a pressure of 74 GPa. Preliminary shock-wave experiments on pure iron preheated to 1300 °C were conducted in the 17-74 GPa range. Melting was observed in the highest pressure (74 GPa) experiment. This result supports our theoretically derived melting curve, which is close to those measured by Boehler (1993) and Saxena et al. (1993).