The melting curve of iron at the pressures of the Earth's core from ab initio calculations

The solid inner core of the Earth and the liquid outer core consist mainly of iron(1) so that knowledge of the high-pressure thermodynamic properties of iron is important for understanding the Earth's deep interior. An accura te knowledge of the melting properties of iron is particularly important, a s the temperature distribution in the core is relatively uncertain(2-4) and a reliable estimate of the melting temperature of iron at the pressure of the inner-core boundary would put a much-needed constraint on core temperat ures. Here we used ab initio methods to compute the free energies of both s olid and liquid iron, and we argue that the resulting theoretical melting c urve competes in accuracy with those obtained from high-pressure experiment s. Our results give a melting temperature of iron of similar to 6,700 +/- 6 00 K at the pressure of the inner-core boundary, consistent with some of th e experimental measurements. Our entirely ab initio methods should also be applicable to many other materials and problems.